Question

the sum of first 10 odd no.is ........​

Answer 1

first 10 odd numbers are.

1,3,5,7,9,11,13,15,17,19.

a = 1

d= 2

l = 19

n = 10

$sn \: = \frac{n}{2} (a + l)$

$sn = \frac{10}{2} (1 + 19)$

$sn = 100$

Answer 2

$first \: 10 \: odd \: numbers \: are \: 1,3,5,7,9,11,13,15,17,19 \\ a = 1 \\ d = 2 \\ i = 19 \\ n = 10 \\ \\ \\ sn = \frac{n}{2} (a + l) \\ \\ sn = \frac{10}{2} (1 + 19) \\ \\ sn = 100$