Question

12, 16, 20
480 is an AP
Find the
sum.​

Answer 1

Answer:

AP= 12,16,20...480

a=12

d=16-12=4

To find n and Sn

An= a+(n-1)d

480=12+(n-1)4

468=n-1(4)

117=n-1

118=n

Therefore there are 118 terms.

Sn= n/2 (2a+(n-1)d)

Sn= 118/2 (2(12)+(117)4)

Sn= 59(24+468)

Sn= 59(492)

Sn= 29028