(5 + 13 + 21 + ... + 181) = ?

Question

KollegeApply · Accepted Answer

2139 Explanation: Let the number of terms be n. Then, Tn = 181. $\therefore$ 5 + (n – 1) $\times$ 8 = 181 $\Rightarrow$ (n – 1) $\times$ 8 = 176 $\Rightarrow$ (n – 1) = 22 $\Rightarrow$ n = 23 $\therefore$ Sum = n/2 (a + l) = $\frac{23}{2}$ (5 + 181) = $\frac{23}{2}$ (186) = 23 $\times$ 93 = 2139

AChoose Your Answer