

The two digit numbers when divided by 4, yields 1 as remainder are:
5, 9,13, 17,................,97
The given series is in A.P.
first term = a =5
common difference = d = 4
Total number of terms in the series
l = a+ (n-1)*d where n is the total number of terms in the series
97 = 5 + (n-1)*4
=>97-5 = (n-1)*4
=>92 = (n-1)*4
=> n-1 = 92/4
=>n-1 = 23
=>n = 23+1
=>n = 24
Now sum of the series = (n/2)*(a+l) (l is the last term of the series)
=>(24/2)*(5+97)
=>12*102
=>1224
