IAS 2025 Success Stories - AIR 1, 11, 27, 39, 53, 67, 73, 77, 88, 89 IAS 2025 Success Stories - AIR 1, 11, 27, 39, 53, 67, 73, 77, 88, 89 IAS 2025 Success Stories - AIR 1, 11, 27, 39, 53, 67, 73, 77, 88, 89
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April 21, 2021 - CSAT Quiz

1. Certain 3-digit numbers have following characteristics:

  1. All the three digits are different.
  2. The number is divisible by 7.
  3. The number on reversing the digits is also divisible by 7.
How many such 3-digit numbers are there? (a) 2 (b) 4 (c) 6 (d) 8 Solution:

There are four such numbers: 168, 861 and 259, 952. To find such numbers first list down all 3 digits divisible by 7. This will generate a large set. In this set remove those whose all digits are not different. Among the remaining ones look for the reverse digits pairings like the two pairs shown here.

(b) 4
 
2. Examine the following statements:
  1. All colours are pleasant.
  2. Some colours are pleasant.
  3. No colour is pleasant.
  4. Some colours are not pleasant.
Given that statement 4 is true, what can be definitely concluded? (a) 1 and 2 are true. (b) 3 is true. (c) 2 is false. (d) 1 is false. Solution: It is given that statement 4 is true i.e. some colours are not pleasant. Now if some colours are not pleasant then its corollary is that some of them are pleasant. Now let us evaluate rest of the three statements:
  1. All colours are pleasant….This is in clear contravention to statement 4 so Statement 1 is false.
  2. Some colours are pleasant….Yes this is true as we found out in the corollary of statement 4.
  3. No colour is pleasant…..No this is false as we found out in the corollary of statement 4.
Thus we know that statement 1 is false, 2 is true and 3 is false. And hence answer choice is (d). (d) 1 is false.   3. How many numbers are there between 99 and 1000 such that the digit 8 occupies the units place? (a) 64 (b) 80 (c) 90 (d) 104 Solution: Numbers are: 108, 118, 128, 138, .............,998 Total = 10 x 9 =90 (c) 90   4. If for a sample data Mean < Median < Mode then the distribution is (a) symmetric (b) skewed to the right (c) neither symmetric nor skewed (d) skewed to the left Solution: A direct question from basic statistics, For a distribution skewed to the left Mean < Median < Mode. Thus the answer is: (d) skewed to the left 5. The age of Mr. X last year was the square of a number and it would be the cube of a number next year. What is the least number of years he must wait for his age to become the cube of a number again? (a) 42 (b) 38 (c) 25 (d) 16 Solution: According to first statement of question his current age is 26 years. (5)2=25←26→27=(3)3 Next cube of a number after 27 = 64 Required difference = 64 – 26 = 38 (b) 38

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