Problem Solving with Percentages | Math Review
In problems involving percentages, it is usually easiest to convert to a fraction or a decimal. For example, to find 40% of 62, convert 40% to either a fraction or a decimal and multiply it times 62. This will give the answer of 24.8.
Computation with Percentages
In problems involving percentages, it is usually easiest to convert to a fraction or a decimal. Let’s look at two examples. First, we’re going to calculate 40 percent of 62. “Of” in math means to multiply. We’re doing 40 percent times 62.
Now we need to convert 40 percent either to a fraction or to a decimal. I’m going to convert it to a decimal. To do that, all I have to do is take my decimal and move it two places to the left. 40 percent as a decimal is 4 tenths, or 40 hundredths, times 62. 4 tenths times 62 is 24 and 8 tenths. 40 percent of 62 is 24 and 8 tenths.
You can use a mental math to find percentages. On this one what we could do is find 10 percent of 62 first and then multiply that times 4 since 10 percent times 4 would be our 40 percent of 62.
To find 10 percent of 62, we would just move the decimal one place to the left so that would be 6 and 2 tenths, and then we want to do that 4 times, so we just multiply that times 4. 6 and 2 tenths times 4 which would again give us 24 and 8 tenths.
This you could do a little easier in your head. Let’s look at one more. Oftentimes percentages are used to calculate the tip when you got to eat at a restaurant. Here we’re going to calculate a 20 percent tip on a 28 dollar and 75 cent meal.
We want to know what 20 percent of 28 dollars and 75 cents since that’s is how much we need to leave them, 20 percent of how much our total bill was. Again, “of” is multiplication, and we want to convert our percent to a decimal so move it two places to left.
We’re really doing 2 tenths times 28 dollars and 75 cents. 2 tenths times 28 dollars and 75 cents is 5 dollars and 75 cents. We would need to leave them a 5 dollar and 75 cent tip.
What would our total bill be? Our total bill would be how much our food costs, plus how much we’re leaving in a tip. 28 and 75 cents, plus 5 dollars and 75 cents. 5 plus 5 is 10, write your 0 carry your 1, 7 plus 7 is 14, plus one is 15, carry your 1, bring down our decimal, 8 plus 1 is 9, plus 5 is 14, write your 4 carry your 1, 2 plus 1 is 3.
Our total bill would be 34 dollars and 50 cents with the tip included.