we have
5 x 4 1/5
remember that
4 1/5=4+1/5=21/5
so
substitute
5x 21/5=21 ------> exact value
An estimate of the product will be
5 x 4 1/5=5 X 4=20
because round 4 1/5 to the nearest whole number
4 1/5=4
therefore
the answer is 20 option C
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