Basic Arithmetic : Linear Equations with Ratios and Rates
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Example Questions
Example Question #13 : Ratios And Rates
I put 
This is a simple interest rate problem, for which we use the formula:
Interest = P x r x t
P is the principal, or original loan amount; r is the annual interest rate; and t is the number of years in question.
In this problem, P = $9,000; r = 4%; and t = 2 years. Plugging these into the formula gives us:
So, after two years the account has gathered $720 in interest.
Example Question #14 : Ratios And Rates
If 
We can set up the following proportions using the given information:
Now, cross multiply these two fractions to get the following equation:
Divide both sides by 
Example Question #15 : Ratios And Rates
If a car travels at 
We can write 40 miles per hour as the following fraction:
Since we want to figure out how many hours it takes a car to travel 200 miles, we can write the following equation:
Now, cross multiply.
Divide both sides by 40.
Example Question #16 : Ratios And Rates
If one recipe calls for 
To solve this problem, we can set up a proportion.
That proportion will tell us how many eggs go into each waffle. Since the number of eggs that goes into each waffle doesn't change, we can set these two proportions equal to each other.
Now, fill it in with the information we know:
For the sake of making math easier, drop the words so we get the following equation:
To solve for x, cross-multiply this equation.
Divide both sides by 18.
Example Question #17 : Ratios And Rates
The ratio of boys to girls in a class is 
We can write the following equation using the ratios given:
Now, we can cross multiply to get the following equation:
Now divide both sides by 
Example Question #21 : Ratios And Rates
Jessica fills an aquarium with water. The aquarium can hold 
The rate at which Jessica fills the tank can be written as a ratio:
Multiply this ratio by the total amount of gallons possible to get the amount of time it takes to fill the tank.
Gallon units cancel out, so you are left with seconds as the final unit in the answer.
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