Joan drive 333.5 miles before she has to buy gas. Her cargets 29miles per gallon. How many gallons of gas did the car star out with ?
Put the fractions upright and try and think about what I am saying
units in fractions can cancel out the same as numbers can
miles/1 * gallons/miles = gallons (because the miles cancel out)
and
29miles per gallon = 29miles/1gallon
If you can go 29 miles on 1 gallon of petrol then
1 gallon of petrol will take you 29miles
So if the rate is 29miles/1gallon it is equivalent to say that the rate is 1gallon/29miles
333.5miles * 1gallon/29miles = 333.5/29 gallons ( the miles cancel out)
I sure other forum users will look at this and say I made a huge deal out of a little problem.
This is true, but if you master this method of dealing with rates you can do all sorts of very difficult rate problems.
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