Question

the first term of an A p is 5 and common difference is 3 then the sum of 20 terms of is
​

Answer 1

Step-by-step explanation:

a=5

c.d=3

sum of Ap= n/2(2a-1)d

n/2 (2*5-1) 3

n/2 (30)

The value of n=15

Answer 2

Answer:

T₁ = a = 5

c.d = 3

S₂₀ = $\frac{n}{2}[2a +(n-1)d]$ = $\frac{20}{2}[2(5)+(20 - 1)3]$

                                  = 10 [ 10 + 57 ]

                         ∴ S₂₀ = 670