Question

10th term of an AP is there are 21 and the sum of its 10th term is 120 find the 20th term of an AP

Answer 1

Answer:

20th term of AP is 41

Step-by-step explanation:

10th term of AP is 21

a₁₀=21

a+9d=21 --->(1)

Sum of first 10 terms=120

s₁₀=120

$\frac{n}{2}$(2a+(n-1)d)=120

5(2a+9d)=120

2a+9d=24 --->(2)

Subtract eq(1) from eq(2)

2a+9d-a-9d=24-21

First term a=3

Substitute in eq(1)

3+9d=21

9d=18

common difference d=2

a₂₀=a+19d=3+19(2)=3+38=41

20th term of AP is 41

Answer 2

Answer:20th term is 41

Step-by-step explanation:

10th term is 21

a+9d=21......›1

S10=120

10/2(2a+9d)=120

5(2a+9d)=120

2a+9d=24........›2

Solve 1&2

a=3,d=2

Now, 20th term

a+19d=3+19(2)

=38+3

=41

So , 20th term is 41