Multiple choice

The average weight of some students in a class was 58.4 kg. When 5 students having the average weight 62.8 kg joined the class, the average weight of all students in the class increased by 0.55 kg. The number of students initially in the class, were:

  1. 30

  2. 35

  3. 25

  4. 40

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let n be the initial number of students. Total weight = 58.4n. After adding 5 students (total weight = 5 × 62.8 = 314), new average = 58.4 + 0.55 = 58.95. So (58.4n + 314)/(n + 5) = 58.95. Solving: 58.4n + 314 = 58.95n + 294.75, which gives 0.55n = 19.25, therefore n = 35.