98 Part 1: The World of Numbers
Ready to make sure you’ve got it? Here are some for you to try.CHECK POINT- George invests $500 in stock and later sells the stock for $650. By what percent
did his investment increase? - Find the percent decrease in Sylvia’s mile time if it was 7.5 minutes when she
began training and now is 6.75 minutes. - Paolo adopted a shelter dog who weighed 8 pounds, but by the next visit to the
vet, the dog weighed 8.5 pounds. Find the percent change in the dog’s weight. - Find the percent decrease in Shawn’s weight if he was 180 pounds when he went
out for the team and now is 150 pounds. - Your favorite brand of ice cream usually comes in a container that holds
1.5 quarts. If the company offers a special container that holds 2 quarts, what is
your percent increase in ice cream?
The Least You Need to Know
- A ratio compares numbers by multiplying or dividing. A proportion is two equal
ratios. A percentage expresses a ratio by comparing to 100. - In any proportion, the product of the means is equal to the product of the
extremes. - Solve a proportion by filling in the known quantities and a variable for the
unknown, cross-multiplying, and dividing. - To solve percentage problems, use the rule
part
whole
%(^5100).
- Simple interest is calculated by multiplying the principal times the rate times the
time. Taxes and tips are calculated as a percentage of the total amount.