Average

Ladakh Police Constable · Mathematics · 56 practice questions with answers and explanations: 18 Easy, 36 Medium, 2 Hard.

Sample questions

Sample Easy question 1

The average weight of 3 people is 55 kg. If two of them weigh 50 kg and 58 kg, find the weight of the third.

  1. 56
  2. 55
  3. 57
  4. 58
Show answer

Answer: C. Total = 55 × 3 = 165. Third person = 165 - 50 - 58 = 57 kg.

Sample Easy question 2

Find the average of all multiples of 5 from 5 to 45.

  1. 25
  2. 23
  3. 27
  4. 22
Show answer

Answer: A. This is an arithmetic sequence from 5 to 45; the average of an AP equals the average of its first and last terms: (5+45)/2 = 25.

Sample Easy question 3

The average of two numbers is 35. If one number is 40, find the other.

  1. 30
  2. 34
  3. 32
  4. 28
Show answer

Answer: A. Sum = 35 × 2 = 70. Other number = 70 - 40 = 30.

Sample Medium question 4

The average age of a family of 5 members is 26 years. If a 10-year-old child is not counted, find the average age of the remaining 4 members.

  1. 29
  2. 30
  3. 32
  4. 31
Show answer

Answer: B. Total age = 5×26 = 130. Excluding the child: (130-10)/4 = 30.

Sample Medium question 5

A car travels from city A to city B at 40 km/h and returns at 60 km/h. Find its average speed for the entire journey.

  1. 50
  2. 48
  3. 52
  4. 46
Show answer

Answer: B. Average speed for a round trip = 2xy/(x+y) = 2×40×60/100 = 48 km/h (not the simple average of the two speeds).

Sample Medium question 6

The average of 7 consecutive numbers is 13. Find the largest number.

  1. 17
  2. 16
  3. 18
  4. 15
Show answer

Answer: B. For consecutive numbers, the average equals the middle term, so the 4th of 7 numbers is 13; the sequence is 10 to 16, and the largest is 16.

Sample Hard question 7

The average of 11 numbers is 50. The average of the first 6 is 49 and of the last 6 is 52. Find the 6th number.

  1. 55
  2. 54
  3. 56
  4. 57
Show answer

Answer: C. Sum of all 11 = 550, first 6 sum = 294, last 6 sum = 312. The 6th number is counted in both: 294 + 312 - 550 = 56.

Sample Hard question 8

The average of 12 numbers is 18. If the average of the first 7 is 20 and the average of the last 6 is 15, find the 7th number.

  1. 15
  2. 17
  3. 14
  4. 16
Show answer

Answer: B. Total of 12 = 216. First 7 total = 140, last 6 total = 90. 7th number is counted in both groups, so 140 + 90 - 216 = 14 — the 7th number is 14.

More Mathematics topics for Ladakh Police Constable

Related articles