Answer:
c.
Step-by-step explanation:
we estimate by rounding the factors to "easy numbers". that means numbers we can easily calculate even in our heads, and we get at just a ballpark number as result for orientation.
59 is much closer to 60 than to 50.
42 is much closer to 40 than to 50.
of course, we round to the closest "round numbers", so that the loss of precision through the rounding is as little as possible, so that the estimation still gives a much value as possible.
and the sum of the differences of the factors should be as close to 0 as possible.
so, 60×40 is the closest and therefore best estimation.
the sum of the factor differences is (+1 - 2) = -1.
compare to the real result :
59×42 = 2,478
answer a and b are by the way not correct :
50×40 = 2000 (and not 2500)
60×50 = 3000 (and not 3500)
FYI - in this case 50×50 = 2500 would be the closest estimation.
and the sum of the factor differences would be (-9 + 8) = -1.
normally, this wide "jumping" (-9 to +8) would make it only second choice.
