Question

Which two consecutive whole numbers is the value of √21 between?
A.4 and 5
B.10 and 11
C.21 and 22
D.42 and 43

Answer 1

The perfect squares on either side of 21 are 16 and 25 of which the roots are:

4 and 5

Answer 2

The answer is:  [A]:  " 4 and 5 " .
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Explanation:
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Looking at the answers:
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 we know that 4² = 16 ; and 5² = 25 ;

So:  √16 = 4  ;  and √25 = 5.

So:  √21 must be between √16 and √25 ;

That is: √21 must be between 4 and 5 ; which is answer choice:  [A] .
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