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The average age of 30 boys in a class is 15 years. One boy, aged 20 years, left the class, but two new boys came in his place whose age differ by 5 years. If the average age of all the boys now in the class becomes 15 years, the age of the younger newcomeris :
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- 20 years
- 15 years
- 10 years
- 8 years
- 20 years
Correct Option: B
According to question ,
Total age of 30 boys = 30 × 15 = 450 years
One boy, aged 20 years, left the class
Now, total age of 29 boys = 450 – 20 = 430 years
Again, two new boys join the class
Then, the total age of 31 boys = 15 × 31 = 465 years
∴ Age of two new boys = 465 – 430 = 35 years
Let the individual age of two boys be p and q years
∴ p + q = 35
According to the question ,
⇒ p – q = 5
∴ 2p = 40
p = 40 ÷ 2 = 20 years
∴ q = 15 years
∴ Age of the younger new comer = 15 years
