Question

last term = 45
a=5

Sn = 400
d=?
(n= ?​

Answer 1

Answer:

use sn formula for this

Step-by-step explanation:

Sn = 400 a =5 an = 45

sn = n/2( a + l )

400 = n/2 ( 5+45)

400= n/2(50)

cross multiply 2 with 400

u get

800 = 50n

n = 800/50

therefore n= 16

use an formula to find d

an = a +(n-1)d

45 = 5 +(16-1)d

45-5= 15d

40= 15d

d = 40/15

divide it by the multiple of 5 and cancel or simplify that gives u

d = 8/3

therefore d = 8/3