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DIRECTIONS for the question: Solve the following question and mark the best possible option.
The value of 1/6 + 1/12 + 1/20 + . . . . . . . . . .. + 1/90 is equal to:
  • a)
    2/5
  • b)
    3/2
  • c)
    4/7
  • d)
    4/5
Correct answer is option 'A'. Can you explain this answer?
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Most Upvoted Answer
DIRECTIONSfor the question:Solve the following question and mark the b...
Consider 1/6 + 1/12 + 1/20 +….. 1/90
= 1/ (2 × 3) + 1/ (3 × 4) + 1/ (4 × 5) +…….. + 1/ (9 × 10)
= 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + ……+ 1/9 –1/10
= 1/2 – 1/10 = 2/5
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DIRECTIONSfor the question:Solve the following question and mark the b...
To solve the given question, we need to find the value of the given series: 1/6, 1/12, 1/20, ..., 1/90.

To find the pattern in the given series, let's first write down the reciprocals of the given numbers:

6, 12, 20, ..., 90

We can observe that these numbers are in an arithmetic progression with a common difference of 6. Therefore, we can rewrite these numbers as:

6, 12, 18, ..., 90

Now, let's write down the reciprocals of these numbers:

1/6, 1/12, 1/18, ..., 1/90

We can observe that these numbers are in a harmonic progression. In a harmonic progression, each term is the reciprocal of an arithmetic progression.

To find the sum of a harmonic progression, we can use the formula:

Sum = (first term) × (1 - (common ratio)^n) / (1 - common ratio)

where the first term is 1/6, the common ratio is 1/6, and n is the number of terms in the series.

Let's calculate the sum:

Sum = (1/6) × (1 - (1/6)^n) / (1 - 1/6)

Since the last term in the series is 1/90, we have a total of 15 terms in the series (from 1/6 to 1/90).

Substituting the values:

Sum = (1/6) × (1 - (1/6)^15) / (1 - 1/6)
= (1/6) × (1 - 1/6^15) / (5/6)
= (1/6) × (1 - 1/470184984576) / (5/6)
= (1/6) × (469184984575/470184984576) / (5/6)
= (1/6) × (469184984575/470184984576) × (6/5)
= 469184984575/470184984576

Simplifying the fraction, we get:

Sum = 1 - 1/470184984576

Therefore, the value of the given series is 469184984575/470184984576.

Comparing this value with the options given, we can see that the correct option is:

a) 2/5

Hence, option A is the correct answer.
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In an MBA entrance exam, questions are classified into two sections - Quants and Verbal. The number of questions in Quants is less than 100 while that in Verbal is not less than 75. Within each section, the questions are classified into Easy or Difficult based on the number of concepts involved. An easy question requires not more than 1 concept, while a difficult question requires 2 or more concepts to solve.Further, a question could be lengthy (atleast 3 minutes to solv e) or non- lengthy (less thanl minute to solve).Based on the following data, answer the subsequent questions.1. The number of difficult, non-lengthy questions in Verbal is 10 less than half the number of easy, non-lengthy questions in Quants.2. The ratio of number of easy, lengthy questions in Quants to number of difficult, lengthy questions in Verbal is 5:3.3. The number of non-lengthy, difficult questions in Quants is 5 less than thrice the number of lengthy, easy questions in Verbal.4. The number of lengthy questions in Verbal is 35 less than the number of easy questions in Quant.5. The number of non-lengthy questions in Quants is 30 more than the number of difficult questions in Verbal.6. The number of easy, non lengthy question in Verbal is thrice the number of lengthy, difficult questions in Quant.7. Each sub-section had atleast 5 questions.Q.Which among the following could be a possible value of total number of easy questions?

In an MBA entrance exam, questions are classified into two sections - Quants and Verbal. The number of questions in Quants is less than 100 while that in Verbal is not less than 75. Within each section, the questions are classified into Easy or Difficult based on the number of concepts involved. An easy question requires not more than 1 concept, while a difficult question requires 2 or more concepts to solve.Further, a question could be lengthy (atleast 3 minutes to solv e) or non- lengthy (less thanl minute to solve).Based on the following data, answer the subsequent questions.1. The number of difficult, non-lengthy questions in Verbal is 10 less than half the number of easy, non-lengthy questions in Quants.2. The ratio of number of easy, lengthy questions in Quants to number of difficult, lengthy questions in Verbal is 5:3.3. The number of non-lengthy, difficult questions in Quants is 5 less than thrice the number of lengthy, easy questions in Verbal.4. The number of lengthy questions in Verbal is 35 less than the number of easy questions in Quant.5. The number of non-lengthy questions in Quants is 30 more than the number of difficult questions in Verbal.6. The number of easy, non lengthy question in Verbal is thrice the number of lengthy, difficult questions in Quant.7. Each sub-section had atleast 5 questions.Q.Find the maximum possible score of the topper, if each correct option fetches 4 marks?

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DIRECTIONSfor the question:Solve the following question and mark the best possible option.The value of 1/6 + 1/12 + 1/20 + . . . . . . . . . .. + 1/90 is equal to:a)2/5b)3/2c)4/7d)4/5Correct answer is option 'A'. Can you explain this answer?
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