Question

Find the sum of all odd number from 1 to 150.

Answer 1

hi..

A.P. = 1 + 3 + 5 + ...................+ 149

here,

a = 1

d = 2

l = 149

first we will find,

a(n) = 149

a + (n-1)d = 149

1 + (n-1) 2 = 149

n-1 = 148/2

n = 74 + 1 = 75

so,

n = 75

sum of n terms = n/2 [2a + (n-1)d]

$s(75) = \frac{75}{2} (2 \times 1 + 74 \times 2)$

$sum = \frac{75}{2} (2 + 148)$

$\frac{75}{2} (150)$

$75 \times 75$

$\bold{ \underline{sum = 5625}}$

$\huge{thank \: u}$