Question

for
an
A.P, a=10 and d=3 then find s15
( Complete the following activity
choose
correct option for
the
empty box)
a= 10
d=3, n=15 s15
. Sn =Ą [2a +(n-0 .]
Sis = 15 [zx10+ (15-1) 3]
S15 = 15 [20414x3
sis
15
돌
sis​

Answer 1

$S_{15} =465$

Step-by-step explanation:

QUESTION

$For \: an \: A.P, \: a=10 \: and \: d=3 \: then \: find \: S_{15}$

___________________________

GIVEN

$a = 10$

$d= 3$

$n = 15$

___________________________

TO FIND

$S_{15}$

___________________________

$We \: know \: that,$

$S = \frac{n}{2} \: (2a + (n - 1) \times d)$

$S = \frac{15}{2} \: (2a + (15 - 1) \times 3)$

$S = \frac{15}{2} \: (2(10) + 14 \times 3)$

$S = \frac{15}{2} \: (20 + 42)$

$S = \frac{15}{2} \times 62$

$S = 7.5 \times 62$

$S =465$

$S_{15} =465$