If a1, a2, a3,...,a15 are in A.P. and a1+a8+a15=15, then a2+a3+a8+a13+a14=
If a1, a2, a3,...,a15 are in A.P., then a2=a1+d, a3=a1+2d,..., where d is the common difference.
⇒a1+a8+a15=3a1+21d=15
⇒a1+7d=5.
a2+a3+a8+a13+a14
=a1+d+a1+2d+a1+7d+a1+12d+a1+13d
=5a1+35d=5(a1+7d)
=5×5=25