SOLUTION: Walking at a constant speed, a person walks 3/4 of a mile every 12 min. How far does the person walk in 30 min? How long does it take the person to walk 2 1/2 miles? (cannot use cr

Question 776077: Walking at a constant speed, a person walks 3/4 of a mile every 12 min. How far does the person walk in 30 min? How long does it take the person to walk 2 1/2 miles? (cannot use cross multiplication in this problem)
Answer by josgarithmetic(39613) (Show Source): You can put this solution on YOUR website!
Rate is miles per minute. This is miles per minute.

First question, let d = unknown distance in miles:

Second question, let t = unknown time in minutes:

You can solve both questions using multiplicative inverse property. Cross multiplication is not needed. The second question is more interesting, and maybe just slightly more complicated ------ but still, you only need the idea of multiplicative inverse.

Start by changing the mixed number into improper fraction:

Next, USE the multiplicative inverse of something and apply to both sides; do you know what/which to choose? You see t as a denominator. What can or do you want to do with this?

As a general example, given y is unknown, and having , the right side contains the multiplicative inverse of y. You can use the multiplicative inverse of the multiplicative inverse of y; which is simply, y.
'

, using multiplicative inverse of

More steps were shown just to help see clearly the process and meaning.
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