Question

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

Answer 1

a+b+c/3=20

a+b+c=60----------eq-1

b+c+d/3=25

b+c+30=75

b+c =45---------eq-2

From eq 1 and 2,

a+45=60

a=60-45

=15