Question

find the sum of all even numbers between 1 and 150

Answer 1

Just apply the summation formula of arithmetic progression

2+4+6…..150

Sum=n/2(first term+last term)

=75/2(2+150)

=75(76)

=5700

Answer 2

Even numbers between 1 and 150 are

2,4,6.....,148

Sum=2+4+6...+148=2(1+2+3+...+74)

=2*(n(n+1))/2=n(n+1)

n=74

Sum=74*75=5550