Interview Q&A / Aptitude

1. A batsman scores 85 runs in his 17th innings and his average goes up by 3. What is his average after the 17th innings?

   37. If the old average was a, then 16a + 85 = 17(a + 3), so a = 34 and the new average is 37. Quick view: 85 covers the new average once plus 3 extra for each of the 16 earlier innings, so new average = 85 - 16 x 3 = 37.

   BeginnerQuick answer1 min read
2. Section A has 30 students with an average of 60 marks and Section B has 20 students with an average of 70. What is the combined average?

   64. Use a weighted average: (30 x 60 + 20 x 70) / 50 = (1,800 + 1,400) / 50 = 3,200 / 50 = 64. It is not 65, because the larger section pulls the average towards 60.

   BeginnerQuick answer1 min read
3. The average of 11 results is 50. The average of the first six is 49 and of the last six is 52. What is the sixth result?

   56. The first six and the last six together count the sixth result twice: 6 x 49 + 6 x 52 = 294 + 312 = 606, while all 11 total 550. The extra 56 is the sixth result.

   BeginnerQuick answer1 min read
4. The average weight of 30 students is 40 kg. When the teacher's weight is included, the average rises by 1 kg. What is the teacher's weight?

   71 kg. New total = 31 x 41 = 1,271 kg; old total = 30 x 40 = 1,200 kg. Teacher = 71 kg. Shortcut: 41 (the new average) + 30 x 1 (raising each student by 1) = 71.

   BeginnerQuick answer1 min read
5. The average age of 8 men rises by 2 years when two of them, aged 21 and 23, are replaced by two women. What is the average age of the women?

   30 years. The group's total rises by 8 x 2 = 16 years. So the women together are 21 + 23 + 16 = 60 years, an average of 30.

   IntermediateQuick answer1 min read