The average weight of some students in a class was 58.4 kg. When 5 students having an average weight of 62.8 kg joined the class, the average weight of all students in the class increase by 0.55 kg. The number of students initially in the class was:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e 35
Let the total no. of students initially be "N".
ATQ,
(A1 + A2 + ............. + AN) / N = 58.4
So, A1 + A2 + ............. + AN = 58.4 × N -------------- Equation 1
Now, the total weight of five new students = 62.8 × 5
= 314 kg
Now, the new average of the whole class after the addition of five new students is :
(A1 + A2 + ............. + AN + 314) / (N + 5) = 58.4 + 0.55
= 58.95
⇒(58.4 N + 314) / (N + 5) = 58.95
⇒ 314 - 294.75 = 0.55N
⇒ N = 35