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The average weight of some members of a club is 70 kg. If 15 members with an average weight of 60 kg join the club or 5 members with an average weight of 90 kg leave the club, then the average weight of members in both cases is equal. How many members were there in the club initially?

The average weight of some members of a club is 70 kg. If 15 members with an average weight of 60 kg join the club or 5 members with an average weight of 90 kg leave the club, then the average weight of members in both cases is equal. How many members were there in the club initially? Correct Answer 45

Given:

The average weight of some members of a club is 70 kg

Concept Used:

Average = Sum of all observation/no of observation

Calculation:

Let x be the members were there in the club initially

According to question

⇒ (70x + 15 x 60)/(x + 15) = (70x - 5 x 90)/(x - 5)

⇒ (70x + 900x)/(x + 15) = (70x - 450)/(x -5)

= (70x2 + 900x - 350x - 4500) = 70x2 - 450x + 1050x - 6750

= (550x - 4500) = (600x - 6750)

= (6750 - 4500) = 50x

= 2250 = 50x

x = 45

Therefore, the members were there in the club initially is 45

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