Find the sum of odd integers from 1 through 57

Step-by-step explanation:

First we find n:

Tn = a + (n-1) d

Here,

a=1, Tn = 57

d=2 (difference between numbers is 2)

Now,

57 = 1 + (n-1) 2

57 = 2n - 1

58/2 = n

Or n = 29

Now, We find sum:

Sn = n/2 { a+Tn}

= 29/2 { 1 + 57 }

= 29/2 (58)

= 29 x 29

= 841