Question

1. Find the sum of the following APs:
fi) 2, 7, 12, ..., to 10 terms.​

Answer 1

Answer:

APs have common difference and here first term or a is 2 and common difference or d is 7 - 2 = 5.

We know nth term = a + ( n - 1 )d

So here,

10th term = 2 + ( 10 - 1 )5

= 2 + (9) 5

= 2 + 45

= 47

Hence 10th term is 47.

And, sum of first 10 terms is

(10/2)( a + 10th term )

= 5 ( 2 + 47 )

= 5 ( 49 )

= 245

Hence sum of first 10 terms is 245.

Answer 2

Answer:

245

Step-by-step explanation:

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

here, n=10, d=7-2=5, a=2

therefore, Sn= 10/2(2×2+9×5)

5×49=245