Question

find the sum of all two digit numbers which when divided by 4,yield 1as remainder

Answer 1

13, 17, 21........... 97

a = 13

d = 4

L = 97

=> a + (n-1)d = 97

=> 13 + (n-1) 4 = 97

=> (n-1)4 = 84

=> n-1 = 21

=> n = 22

S22 = 22/2 [ 2*13 + 21 * 4]

= 11 * ( 26 + 84)

= 11*110

= 1210

Answer 2

13, 17, 21........... 97

a = 13

d = 4

L = 97

=> a + (n-1)d = 97

=> 13 + (n-1) 4 = 97

=> (n-1)4 = 84

=> n-1 = 21

=> n = 22

S22 = 22/2 [ 2*13 + 21 * 4]

= 11 * ( 26 + 84)

= 11*110

= 1210

hope it helped ⚡