Find the sum of all numbers, which are divisible by 8 between

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Find the sum of all numbers, which are divisible by 8 between 200 to 400. ?

1. 7800
2. 7600
3. 7200
4. 7900

Correct Option: A

The least number between 200 and 400, which is divisible by 8 is 200. The last term less than 400, which is divisible by 8 is 400 .
∴ The series is 200, 208, 216,... , 400.
The number of terms in the AP is
(400 - 200/ 8) + 1 = 26
n = 26
d = 8
∴ Sum = n/2[2a + (n - 1) d]
= 26/2 [2x 200 + (26 -1) x 8]
= 13[400 + 200] = 7800