Question 118

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 ofall the students increased by 0.9 kg. The numberofstudentsin theclass,initially, was:

Solution

Let assume initially number of students = $$x$$

Sum of their weight =$$ 60.5 \times x $$

New Average = 60.5 + 0.9 = 61.4

As per question $$ 60.5x + 8\times 65 = 61.4(x + 8)$$

$$\Rightarrow 60.5x + 520 = 61.4x +491.2 $$

$$\Rightarrow 60.5x - 61.4x = 491.2 - 520 $$

$$\Rightarrow -0.9 x = -28.8 $$

$$\Rightarrow x = \dfrac{28.8}{0.9} $$ = 32 Ans

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