(5 + 13 + 21 + … + 181) = ? (a) 2476 (b) 2337 (c) 2219(d) 2139

1.	(5 + 13 + 21 + … + 181) = ? (a) 2476 (b) 2337 (c) 2219(d) 2139
Answer» Correct answer is (d) 2139 Here, a = 5, d = (13 - 5) = 8 and l = 181 Let the number of terms be n. Then, T_n = 181 \(\Rightarrow\) a + (n - 1) d = 181 \(\Rightarrow\) 5 + (n - 1)x8 = 181 \(\Rightarrow\) 8n = 184 \(\Rightarrow\) n = 23 ∴ Required sum = \(\frac{n}{2}(a+l)\) = \(\frac{23}{2}(5+181)=23\times93=2139\) Hence, the required sum is 2139.

Answer»

Correct answer is (d) 2139

Here, a = 5, d = (13 - 5) = 8 and l = 181

Let the number of terms be n.

Then, T_n = 181

\(\Rightarrow\) a + (n - 1) d = 181

\(\Rightarrow\) 5 + (n - 1)x8 = 181

\(\Rightarrow\) 8n = 184

\(\Rightarrow\) n = 23

∴ Required sum = \(\frac{n}{2}(a+l)\)

= \(\frac{23}{2}(5+181)=23\times93=2139\)

Hence, the required sum is 2139.

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