3 years, 7 months ago
3 years, 6 months ago
sum of total boys =12×30=360
if two boys are replaced with average 25 of two boys,
360+sum of replaced boys-replacing boys=sum of new value
360+50-replacing boys sum=12×[30+(5÷6) ]
so we get 410-boys=370
boys sum =40
average of two replacing boys=20