Answer
There are a total of 1,891 combinations.
Explanation
The number of oranges in the third bin is entirely dependant on the
number of oranges in the first and second bin. We will, then, only consider
the first and second bins.
If we put 60 oranges in the first bin, we can put any number of oranges in
the second bin, including zero, up to sixty. Hence there are 61 possibilities
here. If we put 59 oranges in the first bin, we can only put from 1 to 60
oranges in the second bin. There are 60 possibilities here. If we put 58
oranges in the first bin we can put from 2 to 60 oranges in the second bin:
a total of 59 possibilities, and so on. If we put no oranges in the first bin,
we have no choice but to put sixty oranges in the second bin.
The total number of possibilities is the sum of all positive integers from
1 to 61, then, or (61*62)/2 = 61 * 31 = 1,891.
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