Question

The sum of the 8th and 13th terms of an AP is 44 and Ifits 10th term is three times its 3rd
term. Find the sum of 20 terms of the AP​

Answer 1

Answer:

440

Step-by-step explanation:

(a+7d)+(a+12d)=44

2a+19d=44 .....*(1)

a+9d=3(a+2d)

2a-3d=0.......(2)

solving (1)&(2)

22d=44

d=2

2a=3×2

a=3

sum of 20 terms

Sm= n/2(2a+(n-1)d)

Sm =20/2(2×3+19×2)

=10(44)

=440

Answer 2

Step-by-step explanation:

(a+7d)+(a+12d)

2a+19d=44....*(1)

a+9d=3(a+2d)

2a-3d=0.....*(2)

solving (1)and(2)

22d=44

d=2

2a=3×2

a=3

sum of 20 term

sm=n/2(2a+(n-1)d)

sm=20/2(2×3+19×2)

10(44)

440