Question

If the sum of its terms of an ap is 16 and that of 10 terms is 175 find the sum of first n terms.

Answer 1

Step-by-step explanation:

Since,

T(13)=4×T(3)

T(5)=16

We know that a(n)=a+(n−1)d

so

a(13)=a+12d

a(3)=a+2d

By solving this we get

a+12d=4a+8d

a=

3

4

×d

also,

a(5)=a+4d=16

putting value of a we get,

d=3

also

a=4

as we know,

sum (n)=(

2

n

×(a(1)+a(n))

a(10)=4+(9×3)=31

sum(10)=5×(4+31)=175

This is the required answer....

Mark as brainliest