Which term of the A.P. 21, 42, 63, 84, … is 210?
9th
10th
11th
12th
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Here, a = 21, d = 42 - 21 = 21.
Let nth term be 210, so an = 210.
We know that
an = a + (n - 1)d∴ 210 = 21 + (n - 1) × 21⇒ 210 = 21 + 21n - 21⇒ 21n = 210⇒ n = 10
Hence, Option 2 is the correct option.
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