Question

Find the sum of all numbers lying between 50 and 300 divisible by 6.

Answer 1

n(n+1)/2

=300(300+1)/2

=9000+300/2

=9300/2

=4650

n(n+1)=50(50+1)=2500+50=2550

4650-2550=2400

2400 is divisible by6 =400

Answer 2

Answer:

refers to the attachment