Question

please find the answers correctly ​

Answer 1

Answer:  245

Step-by-step explanation:

Clearly, the given sequence is an AP with first term a=2, common difference d=5 and n=10.

Now,  

S  10 =  2 /10  [2a+(10−1)d]

=5[2×2+9×5]

=245

Answer 2

The sum of first 20 terms of Ap

is 2+7+12+.................to 20 terms.

n = 20

a = 2

d = a2-a1,= 7-2= 5.

we have sn= n/2[2a+(n-1)d]

s12 = 20/2 [2(2)+(12-1)5]

= 10[4+(11)5]

= 10[4+55]

= 10[59]

= 590

Therefore the sum of first twenty

terms is 590.