Question
Find the sum of all the two digit numbers, which when divided by 4, yields 1 as remainder.
Solution
All the numbers, which consist of two digits and leave 1 as remainder when divided by 4 are: 13, 17, 21, ........., 97.
Here, a = 13, d = 4,
a + (n - 1)d = 97 13 + (n - 1) 4 = 97
(n - 1) 4 = 97 - 13 = 84 n - 1 = n = 22
∴