Let sum of integers from 1 to 50 that are divisible by 2 and 3 (i.e. 6) is S ∴ S=6+12+18+...+48... (i) {∵ Smallest integerand largest integer divisible by 6 and between 1 and 50 are 6 and 48 respectively} 6,12,18,...,48 (this is an AP) a=6,an=48 and d=6 ∵an=a+(n−1)d ⇒48=6+(n−1)6 ⇒42=(n−1)6 ⇒7=n−1 ⇒n=8 ∴S=