Question

Find the sum of all odd integers between 1 to 100 which are divisible by 3 (step by step pls....)

Answer 1

Hi..

■given

3+9+15.......+99
a=3
d= 6

■to find..
s(n)=?
n=?

■solution:-

▪a(n) = 99
▪a+(n-1)d = 99
▪3 + (n-1)6 = 99
▪n-1 = 96/6
▪n= 16 + 1

$\bold {\boxed{n= 17}}$

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

$= \frac{17}{2} (3 + 99)$

$= \frac{17}{2} \times 102$

$= 17 \times 51$
$= 867$

$\bold{ \boxed{s(n) = 867}}$

#THANKS