Given - sum of all integers between 81 and 719 Formula used - sum of n - number =(n/2)2a+(n−1)×d sum of n- numbers if first and last term are given - (n/2) {a + l} For nth term - Tn=a+(n−1)×d Solution - Let the sum be S. ⇒ integers between 81 and 719 which is divisible by 5 . ⇒ (85, 90, 95, 100, ......................................... 715) ⇒715=85+(n−1)×5 ⇒5×(n−1)=630 ⇒(n−1)=126 ⇒n=127 ⇒S=(127/2)×(85+715) ⇒S=(127/2)×800 ⇒S=50,800 ∴ the sum of the integer between 81 and 719 which is divisible by 5 = 50,800.