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Solving Percent Problems

Ahh…percents. That OTHER topic that is related to fractions that causes so much grief! Well, put that grief aside because I guarantee you 100% that you will soon be able to understand how to 'do' percents!

What do I need to

You need to have a few skills under your belt before you begin:

• Know how to change a fraction to a decimal
• Understand the Commutative Property of Multiplication
• Be familar and comfortable with solving equations with unknowns
• Have the ability to read sentences
Key Words & Symbols

Key words are ALWAYS important, particularly when working out word problems. Identifying the words and translating them into mathematical symbols is half of the battle in making the problem easier to solve. The key words you need to know and their corresponding symbols are:

of means multiply so use
Flow Map: Finding Percents of
The 'out of' Percent Problems

One of the most common types of percent problems is the 'out of' types of problems. Read each of the following.

\165% of what is 15?

Are you struggling with these types of percent problems? If you answered, YES! then go to the 'Out of' Percents page for help.


What's with all the cows? The cow simply helps you to remember to MOOOOOVE the decimal! That's it! It's a mnemonic device. Nothing more, nothing less…

\What is 24% of 82?

Are you stumped yet? Are you thinking, "I need my calculator!" and, then realize, "I don't know what buttons to push!" Don't fret, these are actually really simple IF you remember to moooooo.

What about Simple Interest?

Finding simple interest is actually a VERY good thing to learn because in REAL life, this is one of those things that you will want to learn. As you begin to work and start to save your money, chances are, you will want to open a saving account at a bank or credit union. At banks and credit unions, your money will earn what is called 'interest' which is a percentage of the amount of money you have saved. This is like your money is making money! The longer your money stays in the institution, the more you make (and, the MORE money in the account, the more you make). Once you understand this type of interest, then you need to learn about compound interest (the type for when you want to buy your first car so you need to get a loan…)

See? Here is where learning about percents actually IS important! So, how do you go about computing simple interest? It is actually quite easy.

Problem: graduationcapc

Kim wants to open a savings account for college. She received $750 from her relatives for her birthday. The credit union has a special college account that accrues 4.25% interest. If Kim leaves her money in the account for four years, how much interest will her money earn?

Step 1: Gather your data–P, r, and t

In order to figure our your Interest, you need three pieces of data.
Principle (the amount of money)
rate (this is the percentage)
time (how long it is going to be in the account)

Principle: 750

rate: 4.25%

time: 4 years

Step 2: Write the rate (percent) as a decimal

Change the percent to a decimal by moving the decimal two places to the left.


4.25% = .0425

Step 3: Write your equation I = P • r • t

Write our your equation by substituting your numbers. Interest = P • r • t

I = 750 • .0425 • 4

Step 4: Simplify. That's it!

How simple is that?

I = 31.875 or $31.88

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