Question

The average of a,b,c is 20 and that of b,c,d is 25; of d=30, then the value of a is zigya

Answer 1

a+b+c
$\frac{a + b + c}{3} = 20 \\ \frac{b + c + d}{3} = 25$
d=30
$\frac{b + c + 30}{3} = 25 \\ \\ b + c + 30 = 75 \\ b + c = 45$
$\frac{a + b + c}{3} = 20 \\ a + 45 = 60 \\ \huge\bold{ a = 15}$