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For more on using proportions see;
Welcome to MooMooMath Today we are going to look at setting up proportions.
So lets talk about how you set a proportion.
First will set it up as two fractions that are equal to each other. We have to have the same unit on the top and the matching unit on the bottom.
Once you get you're proportions set up with matching units then you solve it by cross multiplying, so you will multiply top to bottom and top to bottom across.
Next, set these two products equal to each other.
Finally, you just solve the equation.
Lets look at an example of setting up a proportion.
f you are reading a map and the map scale says 1 inch = 2 miles You measure it and 4 1/2 inches = how many miles.
Lets set up a proportion of 1 inch =2 miles the fraction needs to have the same units.
We will set up 4.5 inches/x miles
At this point you can ignore you're units, but you're answer will be in miles.
2 times 4.5 = 1 times x
Grab you're calculator and 2 x 4.5 = 9 so 9 = x and that will be 9 miles.
That is how you set up the proportion.
Set up the units top and bottom, cross multiply, and set them equal to each other and then solve.
Now lets look at some word problems.
The first one is, " The Ford F150 can travel 150 miles on 10 gallons of gas. How much gas is required to travel 150 miles?
We have miles and gallons.
Lets circle the important information.
We have 150 miles and 10 gallons of gas.
150 miles / 10 gallons and set this equal to 750 miles / x gallons of gas
There is my proportion.
Now we just complete a cross product.
150 times x = 10 times 750
Grab you're calculator.
750 x 10 =7500 and divide both sides of the equation by 150 which equals 50
What does 50 represent?
It represents the gallons of gas.
So we will use 50 gallons of gas as our answer to this proportion word problem.
Hope this video was helpful with proportions
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How do you solve problems using proportions
For example: If one inch equals 2 miles, how many miles does 4.5 inches equal?
The video solves the following word problem.
The Ford F150 can travel 150 miles on 10 gallons of gas. How much gas is required to travel 750 miles?
You may also enjoy:
Proportions - Basic examples and word problems
Math Antics - Proportions
Please watch: "Study Skills Teacher's Secret Guide to your Best Grades"
Tagged under: proportions,math,proportion word problems,moomoomath,fraction,fractions,percents,decimals,word problem
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