All questions of L&T for Interview Preparation Exam

There are 6561 balls out of them 1 is heavy. Find the minimum number of times the balls have to be weighed for finding out the heavy ball.
    Correct answer is '8'. Can you explain this answer?

    Ravi Singh answered
    Divide the balls into 3 groups - each of size 6561/3 = 2187.
    Comparing weight of two groups. Now take the heaviest - and sub-divide into 3 more groups 2187/3 = 729
    Take the heaviest - divide into 3 - 729/3 = 243.
    Similarly continue weighing the group of balls.
    Take the heaviest - divide into 3 - 243/3 = 81.
    Take the heaviest - divide into 3 - 81/3 = 27.
    Take the heaviest - divide into 3 - 27/3 = 9
    Take the heaviest - divide into 3 - 9/3 = 3.
    Take the heaviest - divide into 3 - 3/3 = 1.
    So, minimum number of weights = 8

    If I decrease my speed by 20% of original speed, I reach office 7 minute late. What is my usual time and new time of reaching office?
    • a)
      35 minutes
    • b)
      20 minutes
    • c)
      30 minutes
    • d)
      40 minutes
    Correct answer is option 'A'. Can you explain this answer?

    Ravi Singh answered
    Since speed is decreased by 20% i.e. 1/5 of the original. New speed will become 4/5 of the original speed.
    For the same distance, the time will become 5/4 of original time.
    Therefore new time increase by 4 1 of the original.
    This is given equal to 7 minutes.
    So Usual time = 7 - 4 = 28 minutes and New time = 28 + 7 = 35 minutes.

    In a class with a certain number of students if one student weighing 50 kg is added then the average weight of the class increases by 1 kg. If one more student weighing 50 kg is added then the average weight of the class increases by 1.5 kg over the original average. What is the original average weight (in kg) of the class?
    • a)
      46
    • b)
      4
    • c)
      2
    • d)
      47
    Correct answer is option 'D'. Can you explain this answer?

    Kavya Saxena answered
    Let x  be the original average and n be the number of students. Let  x1, x2,  x3 ,. . . .. xn  be the weights of n students respectively. Therefore, 
    Solving (1) and (2), we get
    x + n = 49..... (4)
    Solving (1) and (3), we get
    4x + 3n = 194  ...... (5)
    Now, Solving (4) and (5), we get
    n = 2, x = 47
    So, the original average weight (in kg) of the class = 47
    Alternate Solution :
    Let x be the original average and n be the number of students.
    From the first increase in the average,
    we get 50 - x = n + 1
    From the second increase in the average,
    we get 100 -  2x = 1.5 (n + 2)
    Solving, we get the value of x = 47.

    At the start of a seminar, the ratio of the number of male participants to the number of female participants was 3:1. During the tea break, 16 participants left and 6 more female participants registered. The ratio of the male to the female participants became 2:1. The total number of participants at the start of the seminar was -
    • a)
      64
    • b)
      48
    • c)
      54
    • d)
      Data Insufficient
    Correct answer is option 'D'. Can you explain this answer?

    Aarav Sharma answered
    Given information:
    - Ratio of male participants to female participants at the start of seminar = 3:1
    - 16 participants left during tea break
    - 6 more female participants registered during tea break
    - Ratio of male participants to female participants after tea break = 2:1

    To find:
    - Total number of participants at the start of the seminar

    Solution:
    Let's assume that the ratio of male participants to female participants at the start of the seminar is 3x:1x, where x is a constant.
    - So, the total number of participants at the start of the seminar = 3x + 1x = 4x

    After tea break:
    - The number of male participants remains the same, i.e., 3x
    - The number of female participants becomes 1x+6 (as 6 more female participants registered)

    So, the ratio of male participants to female participants after tea break is 3x:(1x+6) = 2:1
    - Cross-multiplying, we get 3x+18 = 2x
    - Solving for x, we get x = -18

    Here, we get a negative value for x, which is not possible. Hence, the given information is insufficient to find the total number of participants at the start of the seminar.

    Therefore, the correct answer is option D - Data Insufficient.

    A man can row 30 km upstream and 44 km downstream in 10 hours. Also, he can row 40 km upstream and 55 km downstream in 13 hours. The rate of the current is -
    • a)
      3 km/hr
    • b)
      3.5 km/hr
    • c)
      4 km/hr
    • d)
      4.5 km/hr
    • e)
      17
    Correct answer is option 'A'. Can you explain this answer?

    Let rate upstream = x km/hr
    and rate downstream = y km/hr.
    Then,40/x +55/y = 13...(i)
    and 30/x +44/y = 10
    Multiplying (ii) by 4 and (i) by 3 and subtracting ,we get:11/y = 1 or y = 11.
    Substituting y = 11 in (i),
    we get: x = 5.
    Rate in still water =1/2(11+5) kmph = 8 kmph.
    Rate of current=1/2(11-5)kmph = 3 kmph

    A thief steals half the total number of loaves of bread plus 1/2 loaf from a bakery. A second thief steals half the remaining number of loaves plus 1/2 loaf and so on. After the 5th thief has stolen there are no more loaves left in the bakery. What was the total number of loaves did the bakery have at the beginning?
      Correct answer is '31'. Can you explain this answer?

      Aisha Gupta answered
      let y be the total number of loaves
      a be the remaining loaves after 1st thief
      b be the remaining loaves after 2nd thief
      .e = 0 be the remaining loaves after 5th thief
      a = y - 0.5y - 0.5
      = 0.5y - 0.5
      b = a - 0.5a - 0.5
      = 0.5a - 0.5
      c = 0.5b - 0.5
      d = 0.5c - 0.5
      e = 0.5d - 0.5 but e = 0,
      thus,
      d = 1
      c = 3
      b = 7
      a = 15
      y = 31

      In a row of girls, Nivedita is 15th from the left and Vimla is 23rd from the right. If they interchange their positions, then Nivedita becomes 18 th from the left. Then at what position will Vimla be from the right?
      • a)
        26th
      • b)
        22th
      • c)
        24th
      • d)
        28th
      Correct answer is option 'A'. Can you explain this answer?

      Sameer Rane answered
      The situation of positions can be depicted as follows:
       
      ... N (15L) . . . V (23 R) ...
       
      Now, when they interchange their positions, then 
      ... V (?)    . . . N (18 L) ...
       
      So, difference between their positions is 3 (18 - 15). That is, there are 3 people between both of them.
      Thus, Vimla's position from right = 23 + 3 = 26th
       

      A man wears socks of two colours - Black and brown. He has altogether 20 black socks and 20 brown socks in a drawer. Supposing he has to take out the socks in the dark, how many must he take out to be sure that he has a matching pair ?
        Correct answer is '2'. Can you explain this answer?

        Aarav Sharma answered
        Introduction:
        This is a probability problem that requires us to determine the minimum number of socks a man needs to pick from a drawer containing 20 black socks and 20 brown socks in order to be sure that he has a matching pair. Since he is picking socks in the dark, he cannot differentiate between the colors of the socks.

        Understanding the problem:
        To solve this problem, we need to consider the worst-case scenario, where the man picks socks in a way that maximizes the number of different colors he selects before getting a matching pair. We want to find the minimum number of socks he needs to pick to guarantee a matching pair.

        Analysis:
        Let's consider the worst-case scenario where the man picks socks in a way that maximizes the number of different colors he selects before getting a matching pair.

        Step 1:
        In the worst-case scenario, the man can pick any colored sock at his first attempt.

        Step 2:
        In the second attempt, he needs to pick a sock of a different color than the one he picked in the first attempt. This ensures that he has two different colored socks.

        Step 3:
        In the third attempt, he needs to pick a sock of a color that matches one of the two socks he already picked. This guarantees that he has a matching pair.

        Conclusion:
        Therefore, the man needs to pick a minimum of two socks to be sure that he has a matching pair. In the worst-case scenario, he will end up with two different colored socks in the first two attempts and a matching pair in the third attempt.

        The total of the ages of Amar, Akbar and Anthony is 80 years. What was the total of their ages three years ago?
          Correct answer is '71'. Can you explain this answer?

          Aarav Sharma answered
          Question:
          The total of the ages of Amar, Akbar, and Anthony is 80 years. What was the total of their ages three years ago?

          Answer:

          Given Information:
          - The total of the ages of Amar, Akbar, and Anthony is 80 years.

          Let's solve the problem step by step:

          Step 1: Identify the Variables
          - Amar's current age: A
          - Akbar's current age: B
          - Anthony's current age: C

          Step 2: Write the Equations
          - From the given information, we know that A + B + C = 80.

          Step 3: Simplify the Equations
          - There are no further simplifications we can make at this point.

          Step 4: Solve for the Unknowns
          - We need additional information to solve for the unknowns.

          Step 5: Analyze the Question
          - We are asked to find the total of their ages three years ago.

          Step 6: Find Additional Information
          - We need to find the ages of Amar, Akbar, and Anthony three years ago.

          Step 7: Use the Given Information to Find Additional Information
          - Three years ago, Amar's age was A - 3.
          - Three years ago, Akbar's age was B - 3.
          - Three years ago, Anthony's age was C - 3.

          Step 8: Formulate the Answer
          - The total of their ages three years ago would be (A - 3) + (B - 3) + (C - 3).

          Step 9: Simplify the Answer
          - (A - 3) + (B - 3) + (C - 3) = A + B + C - 9.

          Step 10: Substitute Known Values
          - We know that A + B + C = 80 (from the given information).

          Step 11: Calculate the Answer
          - Substituting A + B + C = 80 into the simplified answer:
          (A + B + C - 9) = 80 - 9 = 71.

          Step 12: Formulate the Final Answer
          - The total of their ages three years ago is 71.

          Therefore, the correct answer is 71.

          If CRY is coded as MRYC then how will GET be coded?
          Correct answer is 'METG'. Can you explain this answer?

          Sahil Khanna answered
          Understanding the Coding Pattern
          To decode how "CRY" is transformed into "MRYC," we need to analyze the pattern of the transformation.
          Step-by-Step Analysis
          - The first letter 'C' in "CRY" is moved to the end of the code.
          - The second letter 'R' remains unchanged.
          - The third letter 'Y' becomes 'M' which is four letters back in the alphabet (Y → X → W → V → U → T → S → R → Q → P → O → N → M).
          This transformation follows a pattern of shifting letters and reordering them.
          Applying the Same Pattern to "GET"
          Now let's apply the same transformation to "GET":
          1. Reorder the Letters:
          - Move the first letter 'G' to the end.
          2. Shift the Last Letter:
          - The last letter 'T' needs to be replaced with a letter that is four letters back in the alphabet:
          - T → S → R → Q → P → O → N → M
          3. Resulting Code:
          - After moving 'G' to the end and shifting 'T' to 'M', we get:
          - 'E' remains unchanged.
          - The final arrangement gives us the coded word "METG."
          Conclusion
          Thus, the transformation of "GET" into the code is "METG," following the same pattern established by the initial example.

          If BURNER is coded as CASOIS then how will ALIMENT be coded?
          Correct answer is 'EMONIOU'. Can you explain this answer?

          Aarav Sharma answered
          Code Breakdown:
          In order to find the coded word for "ALIMENT", we need to understand the pattern used to code the word "BURNER" into "CASOIS". Let's break down the given code:

          Original word: BURNER
          Coded word: CASOIS

          - The coded word has the same number of letters as the original word.
          - Each letter in the coded word is obtained by shifting the corresponding letter in the original word by a certain number of positions in the English alphabet.

          Pattern:
          To determine the pattern, we can compare the positions of the corresponding letters in the original and coded words:

          Original word: B U R N E R
          Coded word: C A S O I S

          - The first letter "B" in the original word has shifted one position forward to become "C" in the coded word.
          - The second letter "U" in the original word has shifted one position forward to become "A" in the coded word.
          - The third letter "R" in the original word has shifted one position forward to become "S" in the coded word.
          - The fourth letter "N" in the original word has shifted one position forward to become "O" in the coded word.
          - The fifth letter "E" in the original word has shifted one position forward to become "I" in the coded word.
          - The sixth letter "R" in the original word has shifted one position forward to become "S" in the coded word.

          Applying the Pattern:
          Now that we have identified the pattern, we can apply it to the word "ALIMENT".

          Original word: A L I M E N T
          Coded word: ? ? ? ? ? ? ?

          - The first letter "A" in the original word will shift one position forward to become "B" in the coded word.
          - The second letter "L" in the original word will shift one position forward to become "M" in the coded word.
          - The third letter "I" in the original word will shift one position forward to become "J" in the coded word.
          - The fourth letter "M" in the original word will shift one position forward to become "N" in the coded word.
          - The fifth letter "E" in the original word will shift one position forward to become "F" in the coded word.
          - The sixth letter "N" in the original word will shift one position forward to become "O" in the coded word.
          - The seventh letter "T" in the original word will shift one position forward to become "U" in the coded word.

          Therefore, the coded word for "ALIMENT" is "B M J N F O U" which can be rearranged to form the word "EMONIOU".

          84% of a particular total is 630 marks. What is 90% equal to?
            Correct answer is '675'. Can you explain this answer?

            Aarav Sharma answered
            Explanation:

            To find out what 90% is equal to, we can use the concept of proportion. If 84% is equal to 630 marks, then we can set up a proportion using the following equation:

            84/100 = 630/x

            Here, x represents the total number of marks for 90%. To solve for x, we can cross-multiply and simplify:

            84x = 63000
            x = 750

            So, the total number of marks for 90% is 750. However, the question asks for what 90% is equal to, not the total number of marks. To find out what 90% is equal to, we can use another proportion:

            84/100 = 630/x
            90/100 = y/750

            Here, y represents what 90% is equal to. To solve for y, we can cross-multiply and simplify:

            84x = 63000
            x = 750

            90y = 67500
            y = 750

            So, 90% is equal to 675 marks.

            Calculate the angle between the two hands of clock when the clock shows 5 : 25 p.m.
            • a)
              12.5 degrees
            • b)
              13.5 degrees
            • c)
              14.5 degrees
            • d)
              11.5 degrees
            Correct answer is option 'A'. Can you explain this answer?

            Aisha Gupta answered
            Since at 5 : 25 the minute hand will be at 5 and the angle between them will be same as the distance covered in degree by the hour hand in 25 minutes
            Required angle = distance of hour hand = speed × time = 1/2*25 =12.5 degrees

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