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Question
Which term of the AP: 21, 42, 63, 84,... is 210?
Options
9th
10th
11th
12th
Solution
10th
Explanation:
Let nth term of the given AP be 210
According to question,
First term, a = 21
Common difference, d = 42 – 21 = 21 and an = 210
We know that the nth term of an AP is
an = a + (n – 1)d
Where,
a = first term
an is nth term
d is the common difference
210 = 21 + (n – 1)21
189 = (n – 1)21
n – 1 = 9
n = 10
So, 10th term of an AP is 210.
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