Your teacher might want you to do it as a ratio and proportion
problem:
32 mph means the ratio 32 miles to 1 hour
32 miles is to 1 hour as 128 is to ? hours.
Put an x where the " ? " is:
32 miles is to 1 hour as 128 is to x hours.
"is to" means "over" and "as" means "equals".
32 miles over 1 hour equals 128 miles over x hours.
It's not necessary to write in the units:
Cross-multiply:
32x = 128·1
32x = 128
Divide bth sides by 32.
x =
x = 4
So x hours is 4 hours.
Edwin
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