Step-by-step explanation:
first of all, you could use a calculator and see and compare.
but let's look at this logically :
what fully squared numbers are closest to 42 ?
there is 36 (6²) below, and 49 (7²) above.
so, the solution must be between 6 and 7.
now is 6, 6.5 or 7 closest to the real solution ?
the difference of 6² or 36 to 42 is 6, and the difference of 7² or 49 to 42 is 7.
42 is more or less in the middle.
that means that also the square root will be relatively close to the middle between 6 and 7.
so, 6.5 is the answer.
