Question
Sun February 26, 2012 By:
 

Find the sum, of all natural number between 1 and 100 which is divisible by 3 and 5 both. Also show how the number divisible by 3 and 5 is found out?

Expert Reply
Mon February 27, 2012
Numbers divisible by 3 and 5 both means numbers divisible by 3*5 = 15
So the numbers are 15, 30, 45, ... ,90
Here, a = 15, d = 15 and n = 6
Thus, Sum = (6/3)[30 + 5*15] = 2*105=210
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