1.  The sum of all two digit numbers divisible by 5 is :
A. 945
B. 1035
C. 1245
D. 1230
E. None of these

Answer: Option A

Explanation:

Required numbers are 10, 15, 20, 25, ..., 95

This is an A.P. in which a = 10, d = 5 and l = 95.

tn = 95        a + (n - 1)d = 95

 10 + (n - 1) x 5 = 95

 (n - 1) x 5 = 85

 (n - 1) = 17

 n = 18

Requuired Sum =n(a + l)=18x (10 + 95)   
22

                             = (9 x 105)   = 945.