Question

17th term of AP is 21 more than the 10th term. Find 21st term if 20th term is 50.​

Answer 1

Let the first term of AP be a, and common difference be d.

So,

17th term = a + 16 d

21st term = a + 20d

19th term = a + 18d

10th term = a + 9d

Given,

17th term of AP is 21 more than the 10th term.

So,

⇒a + 16d - 21 = a + 9d

⇒ 16d - 9d = 21

⇒7d = 21

⇒d = 3

Also, 20th term is 50

⇒a + 19d = 50

⇒a + 19(3) = 50

⇒ a = 50 - 57

⇒ a = - 7

Mathematically, 21 term = - 7 + ( 20) (3)=60 - 7 = 53

Or, 21 term = 20 term + d

21 term = 50 + 3 = 53

Therefore, 21st term is 53

Answer 2

Answer:

a21=53

Step-by-step explanation:

by applying some basics, we have calculated the value of a21 as shown in the image