Question

Find the sum of all multiples of 7 between 500 and 900

Answer 1

Multiples of 7 between 500 and 900 are 504,511,518....,896 is in arithmetic progression First term=a=504 Common difference= d =7 Last term=(l)=896 a+(n-1)d=896 504+(n-1)7=896 (n-1)7= 896-504 n-1=392/7 n-1=56 n=56+1 n=57 Sum of 57 terms = n/2*(a+l) =57/2*(504+896) =57/2* 1400 =57*700 =39900