The average weight of some students in a class was 60.5 kg. When 8 students, whose average weight was 65 kg. Joined the class, then the average weight of all the students increased by 0.9kg. The number of students in the class, initially, was:?

40
32
42
37

LohaHridoy

4 views

2025-01-04 04:42

1 Answers

AhmedNazir

Option 2 : 32

Let total number of students be x

Average weight of x students = 60.5 kg

Sum of weight of x students = 60.5x

Average weight of 8 students = 65

Sum of weight of 8 students = 65 × 8 = 520

According to the question

60.5x + 520 = (x + 8)(60.5 + 0.9)

60.5x + 520 = (x + 8) × 61.4

60.5x + 520 = 61.4x + 491.2

61.4x – 60.5x = 520 – 491.2

0.9x = 28.8

x = 28.8/0.9

x = 32

Short Trick :

0.9 kg weight increase for = 1 students

(65 – 60.5) × 8 kg weight increase for = (1/0.9) × 4.5 × 8 = 40 students

Number of students before = 40 – 8 = 32

4 views Answered 2022-09-04 04:29

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