Which term of the AP: 21, 42, 63, 84,... is 210
a. 9th
b. 10th
c. 11th
d. 12th

Solution:

An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. It is obtained by adding the same fixed number to its previous term.

The nth term of an AP is

aₙ = a + (n - 1 )d.

a = first term

aₙ = nth term

d = common difference.

Let the nth term of the given A.P be 210.

As per the question,

first term, a = 21

common difference, d = 42 - 21 = 21.

aₙ = 210.

210 = 21 + (n - 1)21

189 = (n - 1)21

n - 1 = 9

n = 10

Therefore, the 10th term of an AP is 210.

✦ Try This: How can Justin find the 20th term of an AP whose 3rd term is 5 and 7th term is 13

☛ Also Check: NCERT Solutions for Class 10 Maths Chapter 5

NCERT Exemplar Class 10 Maths Exercise 5.1 Problem 8

Which term of the AP: 21, 42, 63, 84,... is 210, a. 9th, b. 10th, c. 11th, d. 12th

Summary:

An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. The 10th term of the AP: 21, 42, 63, 84,... is 210.

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