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All questions of Ratio & Proportion for UPSC CSE Exam

In a bag, there are coins of 25 p, 10 p and 5 p in the ratio of 1 : 2 : 3. If there is Rs. 30 in all, how many 5 p coins are there?
  • a)
    50
  • b)
    100
  • c)
    150
  • d)
    200
Correct answer is option 'C'. Can you explain this answer?

Let x is the number of 25 paisa coins then 2x and 3x will be for 10 and 5 paisa coins. 

Now 30 rupees equal to 30*100 paisa now total paisa equal to x*25+2x*10+3x*5=3000.

60x = 3000.
x = 50.

Now number 5 paisa coin is 3x equal to 3*50 = 150.

An alloy of manganese, tin and bronze contains 90% bronze, 7% manganese and 3% tin. A second alloy of bronze and tin is melted with the first and the mixture contains 85% of bronze, 5% of manganese and 10% of tin. What is the percentage of bronze in the second alloy?
  • a)
    67.5%
  • b)
    72.5%
  • c)
    77.5%
  • d)
    82.5%
Correct answer is 'B'. Can you explain this answer?

Sameer Rane answered
Say M and N are the total volumes of first and second alloys respectively.

Say C, Z and T represent Copper, Tin and Zinc percentages respectively in second alloy.

⇒ C + Z + T = 100 …… Eq.1

Amount of copper in the mixture = 0.90M + (C/100) x N = 0.85 x (M + N)

⇒ 0.05M = (0.85 – C/100) x N

⇒ C = 85 – 5 x (M/N) ….. Eq.2

Amount of Zinc in the mixture = 0.07M + (Z/100) x N = 0.05 x (M + N)

⇒ 0.02M = (0.05 – Z/100) x N

⇒ Z = 5 – 2 x (M/N) ….. Eq.3

Amount of copper in the mixture = 0.03M + (T/100) x N = 0.10 x (M + N)

⇒ –0.07M = (0.10 – T/100) x N

⇒ T = 10 + 7 x (M/N) …… Eq.4

Given Zinc percent in second alloy is Zero

⇒ Z = 0

Eq.3 ⇒ 0 = 5 – 2 x (M/N)

⇒ M/N = 5/2

Substitute M/N = 5/2 in Eq.4

⇒ T = 10 + 7 x (5/2) = 10 + 17.5 = 27.5%

∴ Tin in second alloy = 27.5%

Can you explain the answer of this question below:

Two number are in the ratio 3 : 5. If 9 is subtracted from each, the new numbers are in the ratio 12 : 23. The smaller number is:

  • A:

    27

  • B:

    33

  • C:

    49

  • D:

    55

The answer is B.

Sagar Sharma answered
Given:
The ratio of two numbers is 3:5
After subtracting 9 from each number, the new ratio is 12:23

Let's assume the two numbers in the original ratio are 3x and 5x.

Ratio of the new numbers:
(3x-9) : (5x-9) = 12 : 23

Cross-multiplying, we get:
12(5x-9) = 23(3x-9)

Simplifying the equation:
60x - 108 = 69x - 207
-9x = -99
x = 11

Finding the smaller number:
Smaller number = 3x = 3 * 11 = 33

Therefore, the smaller number is 33, which corresponds to option 'B'.

In a garrison of 3600 men, the provisions were sufficient for 20 days at the rate of 1.5 kg per man per day. If x more men joined, the provisions would be sufficient for 12 days at the rate of 2 kg per man per day. Find x.
  • a)
    600
  • b)
    800
  • c)
    900
  • d)
    720
Correct answer is option 'C'. Can you explain this answer?

Rhea Reddy answered
Let x be the number of new men joined the garrison,
The total quantity of food is = 3600(20) (1.5) kg ----------1
Now the available food will be consumed by (3600+x) men
(3600+x) (12) (2) kg  --------------2
1 = 2
Solving both the equations
3600(20) (1.5) = (3600+x) (12) (2)
108000 = 86400 + 24x
21600 = 24x
X = 900
900 more men joined the garrison.

The sum of four numbers is 253. The ratio of the first number to the second number is 2:3. The ratio of the second number to the third number is 5:6. The ratio of the third number to the fourth number is 8:9. What is the average of the second number and the third number?
  • a)
    72
  • b)
    132
  • c)
    60
  • d)
    66
Correct answer is option 'D'. Can you explain this answer?

Anaya Patel answered
Let the 1stno. A = X
2nd no.= B , 3rd no.= C , 4th no. = D

A: B =2:3
A/B = 2/3
x/B =2/3
B= 3x/2

B:C=5:6
(3x/2)/ C= 5/6
C=( 6×3x)/2×5= 9x/5
C= 9x/5

C:D= 8:9
9x/5/ D = 8/9
D= (9x×9)/8×5= 81x/40
D= 81x/40

A+B+C+D= 253. (GIVEN)
x+ 3x/2+9x/5+81x/40

Lcm = 40
(40x+ 60x+ 72x+81x)/40= 253
253x= 253×40
X= (253×40)/253= 40
Ist no.(A)= X= 40
2no.(B)= 3x/2=( 3 × 40)/2= 60
3rd no.(C)= 9x/5 = (9×40)/5= 72
4th no.(D)= 81x/40=( 81×40/)/40= 81

Average of numbers= sum of observations/ total no.of observations
Average of 2nd no. & 3rd no.= (60+72)/2= 132/2= 66

In a fort there are 1600 soldiers fighting a battle against their enemy. On a particular day after their morning meal the balance provision inside the fort is only sufficient for 12 days at the rate of 1.2 kg per day. If by the evening 400 soldiers die then for how many days will the provision be sufficient for remaining men at the rate of 1.6 kg per day. (Assume soldiers eat either in morning or in evening).
  • a)
    10
  • b)
    8
  • c)
    18
  • d)
    12
Correct answer is option 'D'. Can you explain this answer?

Aarav Sharma answered
Given information:
- Number of soldiers in the fort = 1600
- Provision available for 1 day = 1.2 kg
- Soldiers die in the evening and the remaining soldiers eat 1.6 kg per day

Calculation:
Total provision available in the fort = 1600 x 1.2 x 12 = 23,040 kg
After 400 soldiers die, the remaining soldiers = 1600 - 400 = 1200
The provision required for 1 day by 1200 soldiers = 1.6 x 1200 = 1920 kg
The total provision available after 400 soldiers die = 23,040 - (400 x 1.2) = 22,560 kg
The number of days this provision will last for 1200 soldiers = 22,560 / 1920 = 11.75 days
Since soldiers eat either in the morning or in the evening, we need to round off the answer to the lower integer value, i.e. 11 days.

Therefore, the answer is option 'D' - 12 days.

A man has 25 paise, 50 paise and 1 Rupee coins. There are 220 coins in all and the total amount is 160. If there are thrice as many 1 Rupee coins as there are 25 paise coins, then what is the number of 50 paise coins?
  • a)
    60
  • b)
    80
  • c)
    100
  • d)
    120
Correct answer is option 'A'. Can you explain this answer?

Rajeev Kumar answered
Given:
Total coin = 220
Total money = Rs. 160
There are thrice as many 1 Rupee coins as there are 25 paise coins.
Concept used:
Ratio method is used.
Calculation:
Let the 25 paise coins be 'x'
So, one rupees coins = 3x
50 paise coins = 220 – x – (3x) = 220 – (4x)
According to the questions,
3x + [(220 – 4x)/2] + x/4 =160
⇒ (12x + 440 – 8x + x)/4 = 160
⇒  5x + 440 = 640
⇒ 5x = 200
⇒ x = 40
So, 50 paise coins = 220 – (4x) = 220 – (4 × 40) = 60
∴ The number of 50 paise coin is 60.

Three friends A, B and C started a venture with capitals in the ratio of 4:1:15. At the end of every quarter A halves his capital, while B doubles his capital and C leaves his capital untouched. This process is repeated till the end of the year. If at the end of the year B ’ s share of the profit is Rs 22,000, what is the total profit?
  • a)
    Rs 88,000
  • b)
    Rs 1,10,000
  • c)
    Rs 2,25,000
  • d)
    Rs 1,21,000
Correct answer is option 'D'. Can you explain this answer?

Aarav Sharma answered
Given, ratio of capitals of A, B and C = 4:1:15
Let the initial capitals of A, B and C be 4x, x and 15x respectively.
At the end of the first quarter, their capitals become:
A's capital = 4x/2 = 2x
B's capital = x × 2 = 2x
C's capital = 15x
Their new capital ratio is 2:2:15
Let the new capitals of A, B and C be 2y, 2y and 15y respectively.
At the end of the second quarter, their capitals become:
A's capital = 2y/2 = y
B's capital = 2y × 2 = 4y
C's capital = 15y
Their new capital ratio is 1:4:15
Let the new capitals of A, B and C be z, 4z and 15z respectively.
At the end of the third quarter, their capitals become:
A's capital = z/2
B's capital = 4z × 2 = 8z
C's capital = 15z
Their new capital ratio is 1:8:15
Let the new capitals of A, B and C be m, 8m and 15m respectively.
At the end of the year, the total profit is divided among A, B and C in the ratio of their capitals.
B's share of profit = (8m/24) × Total profit = Rs 22,000
Total profit = (22,000 × 24)/8 = Rs 66,000
Therefore, the total profit is Rs 1,21,000 (option D).

If t : u = 7 : 4, then what is the value of (7t + 4u) : (7t - 4u)?
  • a)
    44 : 23
  • b)
    23 : 45
  • c)
    65 : 33
  • d)
    46 : 25
Correct answer is option 'C'. Can you explain this answer?

Anirudh Joshi answered
Understanding the Ratio
Given the ratio t : u = 7 : 4, we can express t and u in terms of a single variable. Let:
- t = 7x
- u = 4x
where x is a common multiplier.
Calculating 7t + 4u
Now, we substitute t and u into the expression 7t + 4u:
- 7t = 7(7x) = 49x
- 4u = 4(4x) = 16x
Now, adding these:
- 7t + 4u = 49x + 16x = 65x
Calculating 7t - 4u
Next, we compute 7t - 4u:
- 7t = 49x
- 4u = 16x
Now, subtracting these:
- 7t - 4u = 49x - 16x = 33x
Finding the Ratio
Now, we need to find the ratio of (7t + 4u) to (7t - 4u):
- (7t + 4u) : (7t - 4u) = 65x : 33x
The x cancels out, giving us:
- 65 : 33
Final Result
Thus, the value of (7t + 4u) : (7t - 4u) is 65 : 33, which corresponds to option 'C'.

Four numbers in the ratio of 1:3:4:7 add up to give a sum of 75. Find the value of the biggest number.
  • a)
    42
  • b)
    35
  • c)
    49
  • d)
    63
Correct answer is option 'B'. Can you explain this answer?

Kavya Saxena answered
Method to Solve :

Let 1:3:4:7 be 1x, 3x, 4x, 7x respectively.
1x + 3x + 4x + 7x =75
15x = 75
x = 75/15
x = 5
So, 1x = 1*5 = 5
3x = 3*5 = 15
4x = 4*5 = 20
7x = 7*5 = 35

The ratio of two numbers is 2 : 3 and their product is 726. The smallest number between the two numbers is:
  • a)
    22
  • b)
    55
  • c)
    33
  • d)
    11
Correct answer is option 'A'. Can you explain this answer?

Valor Academy answered
Given:
The ratio of two numbers = 2:3
Their product = 726
Formula Used:
Let the numbers be 2x and 3x.
Product of numbers = (2x) × (3x)
Calculation:
Product of numbers = 726
⇒ (2x) × (3x) = 726
⇒ 6x2 = 726
⇒ x2 = 726 / 6
⇒ x2 = 121
⇒ x = √121
⇒ x = 11
Smallest number = 2x = 2 × 11 = 22
The smallest number between the two numbers is 22.

P works twice as fast as Q, whereas P and Q together can work three times as fast as R. If P, Q and R together work on a job, in what ratio should they share the earnings?
  • a)
    2:1:1
  • b)
    4:2:1
  • c)
    4:3:2
  • d)
    4:2:3
Correct answer is option 'A'. Can you explain this answer?

Akanksha Datta answered
If P is taking 3 days to do some work, then Q takes 6 days to do the same work. Now, both of them will take 2 days to complete the work. So, R takes 6 days to complete the same work.
Hence, earning should be distributed in the ratio of their efficiency, i.e., 2 : 1 : 1.

Two numbers are 30% and 20% less than a third number respectively. The ratio of first two numbers is:
  • a)
    7 : 6
  • b)
    3 : 2
  • c)
    7 : 8
  • d)
    8 : 7
Correct answer is option 'C'. Can you explain this answer?

Given:
Two numbers are 30% and 20% less than a third number respectively.
Formula Used:
If a number is x% less than another number, then it is equal to (100 - x)% of that number.
Ratio = First number / Second number
Calculation:
Let the third number be 100.
First number = 100 - 30% of 100
First number = 100 - 30
First number = 70
Second number = 100 - 20% of 100
Second number = 100 - 20
Second number = 80
Ratio of the first two numbers = First number / Second number
⇒ Ratio = 70 / 80
⇒ Ratio = 7 / 8
The ratio of the first two numbers is 7 : 8.

A man has rs.480 in the denominations of one-rupee notes, five-rupee notes and ten-rupee notes. The number of notes of each denomination is equal. What is the total number of notes that he has ?
  • a)
    100
  • b)
    50
  • c)
    78
  • d)
    90
Correct answer is option 'D'. Can you explain this answer?

Aisha Gupta answered
 Given that a man has Rs. 480 in the denominations of one-rupee notes, five-rupee notes and ten-rupee notes. The number of notes of each denomination is equal.
We are to find the total number of notes he has.
Let x represents the number of notes of each of the three denominations.
Then, according to the given information, we have

Two numbers are in the ratio 2:5. If 6 is added to both, their ratio changes to 4:7. What is the larger number?
  • a)
    6
  • b)
    12
  • c)
    15
  • d)
    21
Correct answer is option 'C'. Can you explain this answer?

Mihir Mehta answered
Understanding the Problem
We have two numbers in the ratio 2:5. Let's denote these numbers as:
- First Number = 2x
- Second Number = 5x
After adding 6 to both numbers, their ratio changes to 4:7.
Setting Up the Equation
When we add 6 to both numbers, we can express the new situation as:
- New First Number = 2x + 6
- New Second Number = 5x + 6
According to the problem, the new ratio is:
(2x + 6) / (5x + 6) = 4/7
Cross-Multiplying to Solve
To eliminate the fraction, we can cross-multiply:
7(2x + 6) = 4(5x + 6)
This simplifies to:
14x + 42 = 20x + 24
Rearranging the Equation
Next, we rearrange it to isolate x:
14x - 20x = 24 - 42
This gives us:
-6x = -18
Thus, we find:
x = 3
Finding the Numbers
Now that we have x, we can find the original numbers:
- First Number = 2x = 2(3) = 6
- Second Number = 5x = 5(3) = 15
Conclusion
The larger number is:
- 15
Thus, the correct answer is option 'C'.

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