CSAT 2020

1. The minimum number of points of intersection of a square and a circle is 2. 2. The maximum number of points of intersection of a square and a circle is 8.

Q. Consider the following statements:

1. The minimum number of points of intersection of a square and a circle is 2.
2. The maximum number of points of intersection of a square and a circle is 8.

Which of the above statements is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Correct Answer: (b) 2 only

Question from UPSC Prelims 2020 CSAT Paper

Explanation :

Minimum number & maximum of points of intersection of a square and circle

Statement 1 is incorrect. The minimum number of points of intersection between a square and a circle can be 0 if the circle is entirely inside or outside the square.

Statement 2 is correct. The maximum number of points of intersection between a square and a circle is 8. This can happen when the circle passes through all four corners of the square and intersects each side once.

So only statement 2 is correct. Therefore, the correct answer is indeed (b) 2 only.

1. The minimum number of points of intersection of a square and a circle is 2. 2. The maximum number of points of intersection of a square and a circle is 8. Read More »

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4?

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4?

(a) 2n
(b) 3n
(c) 2n + 4
(d) 3n+ 1
Correct Answer: (d) 3n+ 1

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

Digit n > 3 is divisible by 3

Since n is divisible by 3 but not divisible by 6, it means that n must be an odd multiple of 3. Let’s take n=9 as an example.

(a) 2n = 2 * 9 = 18 which is not divisible by 4

(b) 3n = 3 * 9 = 27 which is not divisible by 4

(c) 2n +4 = (2 *9) +4 =22 which is not divisible by 4

(d) 3n +1 = (3 *9)+1=28 which is divisible by 4

So the correct answer is (d) 3n+1.

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4? Read More »

Q. A bottle contains 20 litres of liquid A.

Q. A bottle contains 20 litres of liquid A.

4 litres of liquid A is taken out of it d replaced by same quantity of liquid B. Again 4 litre of the mixture is taken out and replaced by same quantity of liquid B. What is the ratio of quantity of liquid A to that of liquid B in the final mixture?

(a) 4:1
(b) 5:1
(c) 16:9
(d) 17: 8
Correct Answer: (c) 16:9

Question from UPSC Prelims 2020 CSAT Paper

Explanation :

PROBLEM: Find the final ratio of liquids A and B after two replacements

STEP 1: After First Replacement
– Liquid A = 16 litres
– Liquid B = 4 litres
– Total = 20 litres
– Ratio of A to total = 16/20 = 4/5

STEP 2: Second Replacement
– 4 litres mixture removed
– Liquid A removed = 4 × 4/5 = 3.2 litres
– Liquid A remaining = 16 – 3.2 = 12.8 litres
– Liquid B = 20 – 12.8 = 7.2 litres

STEP 3: Final Ratio
12.8:7.2 simplifies to 16:9

ANSWER: The final ratio of liquid A to liquid B is 16:9

Q. A bottle contains 20 litres of liquid A. Read More »

Q. In adult population or a city, 40% men and 30% women are married.

Q. In adult population or a city, 40% men and 30% women are married.

What is the percentage of married adult population if no man marries more than one woman and no woman marries more than one man; and there are no widows and widowers?

(a) 232/7%
(b) 34%
(c) 240/7%
(d) 35%
Correct Answer: (c) 240/7%

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

PROBLEM: Find percentage of married adults in population

GIVEN:
– 40% men are married
– 30% women are married
– Each marriage has one man and one woman

SOLUTION:
Let M = number of men
W = number of women

1. Since married men = married women:
0.4M = 0.3W
W = (4/3)M

2. Total Population N = M + W = M + (4/3)M = (7/3)M

3. Total married adults = 0.4M + 0.3W
= 0.4M + 0.3(4/3)M
= 0.8M

4. Percentage = (0.8M)/(7/3)M = (0.8 × 3)/7 = 2.4/7
= 240/7%
≈ 34.29%

ANSWER: 240/7% or approximately 34.29%

Q. In adult population or a city, 40% men and 30% women are married. Read More »

Q. What is the missing @ term in the following?

Q. What is the missing @ term in the following?

ACPQ : BESU:: MNGI: @

(a) NPJL
(b) NOJM
(c) NPIL
(d) NPJM
Correct Answer: (d) NPJM

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

acpq: besu:: mngi: @

PATTERN: ACPQ → BESU
Letter Shifts:
– 1st letter: +1
– 2nd letter: +2
– 3rd letter: +3
– 4th letter: +4

Starting Word: MNGI
Applying shifts:
M + 1 = N
N + 2 = P
G + 3 = J
I + 4 = M

ANSWER: NPJM

Q. What is the missing @ term in the following? Read More »

Q. The letters from A to Z are numbered from 1 to 26 respectively. If GHI = 1578 and DEF = 912, then what is ABC equal to?

Q. The letters from A to Z are numbered from 1 to 26 respectively. If GHI = 1578 and DEF = 912, then what is ABC equal to?

(a) 492
(b) 468
(c) 262
(d) 246
Correct Answer: (d) 246

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

ghi=1578 def=912 abc= ?

ALPHABETS TO NUMBERS:
ABC = 123
DEF = 456
GHI = 789

DOUBLING THE NUMBERS:
ABC: 123 × 2 = 246
DEF: 456 × 2 = 912
GHI: 789 × 2 = 1578

Pattern: Each three-letter group when doubled gives the result shown on the right side.

Q. The letters from A to Z are numbered from 1 to 26 respectively. If GHI = 1578 and DEF = 912, then what is ABC equal to? Read More »

Q. If 1 litre of water weighs 1 kg, then how many cubic millimeters of water will weigh 0.1 gm?

Q. If 1 litre of water weighs 1 kg, then how many cubic millimeters of water will weigh 0.1 gm?

(a) 1
(b) 10
(c) 100
(d) 1000
Correct Answer: (c) 100

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

If 1 litre of water weighs 1kg ….

GIVEN CONVERSIONS:
1. Volume Conversion:
– 1 cubic millimeter = 10^-6 liters
– 1 liter = 10^6 cubic millimeters

2. Weight-Volume Relationship:
– 1000 grams (1 kg) = 10^6 cubic millimeters

CALCULATION:
1. To find volume for 0.1 grams:
– If 1000 grams = 10^6 cubic millimeters
– Then 1 gram = 10^3 cubic millimeters
– Therefore, 0.1 grams = 10^2 cubic millimeters
– 0.1 grams = 100 cubic millimeters

Q. If 1 litre of water weighs 1 kg, then how many cubic millimeters of water will weigh 0.1 gm? Read More »

Q. Three Statements S1, S2 and S3 are given below followed by a Question:  S1: C is younger than D, but older than A and B.  S2: D is the oldest.  S3: A is older than B. 

Q. Three Statements S1, S2 and S3 are given below followed by a Question:

S1: C is younger than D, but older than A and B.
S2: D is the oldest.
S3: A is older than B.

Question: Who among A, B, C and D is the youngest?
Which one of the following is correct in respect of the above Statements and the Question?
(a) S1 alone is sufficient to answer the Question.
(b) S1 and S2 together are sufficient to answer the Question.
(c) S2 and S3 together are sufficient to answer the Question.
(d) S1 and S3 together are sufficient to answer the Question.
Correct Answer: (d) S1 and S3 together are sufficient to answer the Question.

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

C is younger than D

From statement S1 we know that C is younger than D but older than A and B. So the order of their ages is: D > C > A and B.

From statement S3 we know that A is older than B. Combining this information with statement S1, we get the order of their ages as: D > C > A > B.

So from statements S1 and S3 together, we can conclude that B is the youngest among A, B, C and D

Q. Three Statements S1, S2 and S3 are given below followed by a Question:  S1: C is younger than D, but older than A and B.  S2: D is the oldest.  S3: A is older than B.  Read More »

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4?

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4?

(a) 2n
(b) 3n
(c) 2n + 4
(d) 3n+ 1
Correct Answer: (d) 3n+ 1

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

Digit n > 3 is divisible by 3

Since n is divisible by 3 but not divisible by 6, it means that n must be an odd multiple of 3. Let’s take n=9 as an example.

(a) 2n = 2 * 9 = 18 which is not divisible by 4

(b) 3n = 3 * 9 = 27 which is not divisible by 4

(c) 2n +4 = (2 *9) +4 =22 which is not divisible by 4

(d) 3n +1 = (3 *9)+1=28 which is divisible by 4

So the correct answer is (d) 3n+1.

Q. A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4? Read More »

Q. Which one of the following will have minimum change in its value if s is added to both numerator and the denominator of the fractions 2/3, 3/4, 4/5 and 5/6? 

Q. Which one of the following will have minimum change in its value if s is added to both numerator and the denominator of the fractions 2/3, 3/4, 4/5 and 5/6?

(a) 2/3
(b) 3/4
(c) 4/5
(d) 5/6
Correct Answer: (d) 5/6

Question from UPSC Prelims 2020 CSAT Paper

Explanation : 

Let’s solve this step by step:

PROBLEM: Finding which fraction has minimum change when s is added to both numerator and denominator

ORIGINAL FRACTIONS:
2/3, 3/4, 4/5, 5/6

NEW FRACTIONS AFTER ADDING s:
(2 + s)/(3 + s)
(3 + s)/(4 + s)
(4 + s)/(5 + s)
(5 + s)/(6 + s)

CHANGES IN VALUE:
|2/3 – (2 + s)/(3 + s)|
|3/4 – (3 + s)/(4 + s)|
|4/5 – (4 + s)/(5 + s)|
|5/6 – (5 + s)/(6 + s)|

ANALYSIS:
1. When s becomes very large:
– The numerator terms (2,3,4,5) become negligible
– The denominator terms (3,4,5,6) become negligible
– All fractions approach s/s = 1

2. Original values:
2/3 ≈ 0.667
3/4 = 0.750
4/5 = 0.800
5/6 ≈ 0.833

3. Since all fractions approach 1:
– The fraction closest to 1 will have minimum change
– 5/6 is closest to 1 among all given fractions

CONCLUSION: The fraction 5/6 will have the minimum change in value when s is added to both numerator and denominator.

Q. Which one of the following will have minimum change in its value if s is added to both numerator and the denominator of the fractions 2/3, 3/4, 4/5 and 5/6?  Read More »