SOLUTION: A group of 30 children shared some stamps among themselves. 1/3 of the children received 5 stamps each. 3/5 of them received 10 stamps each and the rest received 15 stamps each.

 
That's 1/3 of 30 children, which is 10 children

So those 10 children altogether received 10x5=50 stamps.

That's 3/5 of 30 children, which is 18 children

So those 18 children altogether received 18x10=180 stamps.

Let's see what fraction is the rest. We've already talked about 1/3 of them 
plus 3/5 of them:



The least common denominator is 15.





So we've already talked about 14/15ths, so the rest is 1/15th:

That's 1/15 of 30 children, which is 2 children

So those 2 children together received 2x15=30 stamps.

So we add them up.   50 + 180 + 30 = 260 stamps.

Edwin

 of the 30 children, or  = 10 children received 5 each, or a total 10(5) = 50 stamps

 of the 30 children, or  = 18 children received 10 each, or a total 18(10) = 180 stamps

The remaining 2 (30 - 10 - 18) children received 15 each, or a total 2(15) = 30 stamps

Total number of stamps: 50 + 180 + 30 = 260