Question

The sum of a series ;27+36+45+?+16227+36+45+?+162 is 15121512

Answer 1

a1=27
a2=36
a3=45
common difference(D) =a2-a1
=36-27
= 9
a4= a+3d
= 27+3×9
= 54
a8= a+7d
=27+7×9
=90