Question

2+7+12........find the sum of first 20 terms​

Answer 1

Step-by-step explanation:

2+7+12+..

is in AP with a=2, d=5

sum = n/2(2a+(n-1)d)

= 20/2 ×(2×2 + (20-1)×5) = 10×(4+95) = 990

Answer 2

Step-by-step explanation:

We know that

Sum of AP= n/2(2a+(n-1)d)

Here n=20, a=2

and d=7-2=5

Putting these in formula ,

Sum =n/2(2a+(n-1)d)

= 20/2 (2×2+(20-1)×5)

=10(4+19×5)

=10(95+4)

=10(99)

=990.