Find the Sum of those integers between 1 and 500 which are multiples of 2 as well as of 5.


Since, multiples of 2 as well as of 5 = LCM of (2, 5) = 10


Multiples of 2 as well as of 5 between 1 and 500 is 10, 20, 30, …., 490.


Clearly this is an AP with common difference, d = 10


And first term, a = 10


Let the no if terms in this AP are n


Then, by nth term formula


an = a + (n - 1)d


490 = 10 + (n - 1)10


480 = (n - 1)10


n - 1 = 48


n = 49


now, Sum of this AP


[ as last term is given]




= 49(250)


= 12250


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