Percent Change & Percent Error
A gym had 8,500 members in 2012. It now has 7,000 members. What is the percent change?
17.6% decrease
(#5a) Noah has a coupon for 30% off at his favorite clothing store. He uses it to buy a hoodie and pair of jeans.
Noah paid $28 for the jeans after using the coupon. What is the regular price of the jeans?
100% - 30% = 70%
70%/100 = 0.7
0.7 * x = 28
28 / 0.7 = $40
A jacket costs $68. Laura has a 20% off coupon and pays 8% tax. What is her total cost?
Sale price = 54.40 Total = 54.40 × 1.08 = $58.75
A snail crawls 2 1/2 inches in 3/4 of an hour. What is the snail's speed?
Inches per HOUR so divide by HOURS
2 1/2 divided by 3/4 = 5/2 * 4/3 = 20/6 = 3 2/6
= 3 1/3 inches per hour
A house price dropped from $180,000 to $165,000. What is the percent change?
8.33% decrease
The regular price of a hoodie is $54. If Noah has a 25% off coupon, how much money did he pay for the hoodie?
100% - 25% = 75%
75% / 100 = 0.75
0.75 * 54 = $40.50
Starbucks surveyed 1230 customers. If 70% prefer iced peppermint mochas, how many customers is that?
0.70×1230=861 861
To make a shade of paint called navy blue, mix 3 quarts of blue paint with 2 2/3 cups of orange paint. How much blue paint should be mixed with 6 cups of orange paint to make navy blue?
3 divided by 2 2/3 = 3 divided by 8/3 = 3/1 * 3/8 = 9/8
6 * 9/8 = 6/1 * 9/8 = 54/8 = 6 6/8 = 6 3/4 blue paint
Marcus estimated 230 people would attend a concert. Actual attendance was 300. What is the percent error?
300 - 230 = 70 people off (error)
x * 300 = 70
70/300 = 0.2333333 * 100 = 23.3%
(#7a) Jada's sister earn $15 per hour. The store offers her a raise - a 9% increase. After the raise, how much will Jada's sister make per hour?
100% + 9% = 109%
109% / 100 = 1.09
1.09 * 15 = $16.35 per hour
A restaurant bill is $73.89 with 7.25% tax and a 15% tip. What is the total bill?
After tax: 79.23 After tip: 91.12 $91.12
(#3) It takes Diego 1/24 of an hour to complete a lap on a circular bike track. The track is 1/3 mile long. What is Diego's bike speed?
Speed is MILES per HOUR. Divide by your HOURS
1/3 divided by 1/24 = 1/3 * 24/1 = 24/3 = 8mph
A meteorologist predicts that a town will receive 8 inches of snow. The town actually gets 10 inches. What was the percent error of the forecast?
10 - 8 = 2 inches off (error)
x * 10 = 2
2/10 = 0.2 * 100 = 20% measurement error
(#7b) The store buys a table for $200 and sells it for $350. What percentage is the mark-up?
x * 200 = 350
350/200 = 1.75 * 100 = 175%
175% - 100% = 75%
Marked up by 75%
(#6) Kiran's mother gets a restaurant bill for $25. She has a coupon for 15% off. After the discount is applied, she adds 20% as a tip. What is the total after the discount and tip?
100% - 15% = 85%
85% / 100 = 0.85
0.85 * 25 = $21.25
Next... 100% + 20% = 120%
120% / 100 = 1.2
21.25 * 1.2 = $25.50
(#1) Clare has a recipe for yellow cake. She uses 9 1/3 cups of flour to make 4 cakes. Noah will follow the same recipe. He will make c cakes using f cups of flour. Which of these equations represent the relationship between c and f?
f times _____ = c sooo
9 1/3 times _____ = 4
When you don't know what to multiply, divide to figure it out!
4 divided by 9 1/3 = 4/1 divided by 28/3 = 4/1 * 3/28 = 12/28
Simplify by finding what number divides both 12 and 28 which is 4!!! So you end up with 3/7
c = 3/7f
(#2) A graduated cylinder actually contains 7.5 milliliters of water. What Han measures the volume of the water inside the graduated cylinder, his measurement is 7 milliliters. Which of these is the closest to the percent error for Han's measurement?
7.5 - 7 = 0.5 milliliters off (error)
x * 7.5 = 0.5
0.5/7.5 = 0.066666 * 100 = 6.66666 which is about 6.7%
(#7c) Jada's sister earns a commission that is 3.5% of the amount she sells. Last week she sold $7,000 worth of furniture. How much was her commission?
3.5% / 100 = 0.035
0.035 * 7000 = $245
A refrigerator is discounted 30%. After tax of 8.25%, the final price is $1,047. What was the refrigerator’s original price?
Before tax...
100% + 8.25% = 108.25% --> 1.0825
1.0825 * x = 1,047
1,047 / 1.0825 = $967.21
Now before discount...
100% - 30% = 70% --> 0.7
0.7 * x = 967.21
967.21 / 0.7 = $1381.73
At a deli counter,
Someone bought 1 3/4 pounds of ham for $14.50.
Someone else bought 2 1/2 pounds of turkey for $26.25.
Which meat is least expensive?
14.50 / 1.75 = 8.29 per pound
26.25 / 2.5 = 10.50 per pound
Ham is less expensive!