Step-by-step answer:
Question requests use of mental math.
When calculating 45%, we use the fact that 45% is 90% of 50%, or
45% can be obtained by subtracting 1/10th of half the amount.
Thus 45% of $120 is obtained by
subtracting 1/10th of half of $120, which is
subtract 1/10th of $60
which in turn gives 60-6 = $54.
no calculator is required.
