posted by Chayo on .
Use a proportion to solve the problem.
Under typical conditions, 1 1/2ft of snow will melt to 2 in. of water. To how many inches of water will 3 1/4 ft of snow melt? Express your answer as an integer or mixed number.
x/(13/4) = 2/(3/2)
(3/2)x = 2(13/4)
x = (13/2)(2/3)
= 13/2 or 6 1/2
Start by converting mixed numbers into improper fractions.
1 1/2ft = 3/2 ft.
3 1/4ft = 13/4 ft
Now divide 2in by 3/2 ft
2/(3/2) = 4/3
So, if 3/2 feet of snow yields 2 in of water, 1ft of snow will yield 4/3 in of water.
Now multiply 13/4 by 4/3.
13/4*4/3 = 13/3. Convert that to a mixed number: 4 1/3.
3 1/4ft of snow will melt to 4 1/3 in of water.
Marth is correct, my last line should have been
= 13/3 or 4 1/3
Argghhh!, silly arithmetic errors
So what your trying to say is that I always convert my mixed numbers into imporper fractions that is my first step right? Once I have done that I divide but is it always going to be divided by two or it depends on the problem. Last but not least is mult. so the steps are convert mixed #'s, divide, then mult.
mixed numbers are pretty well useless in actual calculations, since the first thing one usually has to do is change them to improper fractions.
I also resent the fact that something like 5/2 is called an "improper" fraction, there is nothing improper about them.
I never really cared if my students left final answers in mixed fraction form or 'improper' fraction form.
What I do resent is that some teachers mark it "wrong" if you don't change it to a mixed fraction.