Question 853613
One way to think of it is:
Suppose you give 5 apples to 5 people
Each person gets 1 apple
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Now suppose you want to take away 1 apple
so that each person still has the same share
That means you take away 1/5 of an apple
from each person
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Now take away 1 more apple leaving each 
person with the same share
So, you take away 1/5 of an apple 
from each person again
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Now the 5 people have {{{ 5 - 2 = 3 }}} apples
and each person has {{{ 1 - 1/5 - 1/5 }}}
{{{ 1 - 2/5 = 3/5 }}}, so each person ends up with 
3/5 of an apple
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Hope this helps