KnowledgeBoat Logo
|

Mathematics

Find the sum of 28 terms of an A.P. whose nth term is 8n - 5.

AP

50 Likes

Answer

Given,

an = 8n - 5

So,

a1 = 8(1) - 5 = 3,

a28 = 8(28) - 5 = 219.

S=n2(a+l)=282(3+219)=14×222=3108.S = \dfrac{n}{2}(a + l) \\[1em] = \dfrac{28}{2}(3 + 219) \\[1em] = 14 \times 222 \\[1em] = 3108.

Hence, sum = 3108.

Answered By

22 Likes


Related Questions