Question

1) Find the sum of 5, 10, 15, .... upto 45 terms​

Answer 1

Answer:

a=5 , n=45, d=10-5=5

s=n/2[2a+(n-1)d]

s=45/2[2×5+(45-1)5]

=45/2[10+220]

=45/2[230]

=45×230/2

=45×115

=5175