Question

Please answer this 2 question​

Answer 1

Explanation:

AP 1 : 12, 15 , 18 , 21, 24, 27, 30 , 33 , 36, 39,.....

AP 2 : 17 , 21 , 25 , 29, 33, 37 , 41, 45,.....

AP formed with the common terms: 21, 33, 45 , ......

a = 21 , d = 33-21 = 12 ; n = 100

Sum =
`(n)/(2)(2a +(n-1)d)`

`=(100)/(2)[2*21+99*12]\\\\=50 * [42+1188]\\\\=50*1230\\\\= 61500`