Question

If 8th term of an ap is 15 then sum of 15 terms is

Answer 1

Answer:

Sum of 15 terms = 225

Step-by-step explanation:

(a8) = a + 7d = 15 ---- Eq 1

Sum of 15 terms = (n/2)(2a + 14d) ----- Eq 2

Multiplying Eq 1 by 2,

2a + 14d = 30

Substituting the above in Eq 2,

Sum of 15 terms = (n/2)(30) =

$\frac{15}{2} \times 30 = 15 \times 15 = 225$