Question

If two sets a and b have 99 elements in common, then the number of elements common to sts a*b and b*a

Answer 1

a and b having 99 elements in common.

Then number of elements common to each sets a ✖ b and b ✖ a = 99 ✖ 99
=(99) ² = 9801

Actually you can see 99 elements which are common to both a and b in 99 ways separately in both the cases.
And when you will multiple these you will get the same number of elements

Eg, a ✖ b = (99)² and b ✖ a = (99)²

So, the answer should be 99² = 9801

Hope it helps
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