WorksheetsKPrep Review11-Percent of Change &Random Sampling
Total questions: 20
Worksheet time: 5hrs 0mins
In January, Jamie pays $2.00 for a tube of toothpaste. When she buys the same brand and size toothpaste in February, she pays $2.25. What is the percent of increase in the price of the toothpaste from January to February?
89%
12.5%
13%
12%
A company conducts a study of how its number of employees has changed over three years. At the beginning of the three-year period, the company had 240 employees. The table shows the percent change in the number of employees during each year that followed. Select the true statements.
There were 216 employees at the company at the end of Year 1.
The company had 270 employees at the end of Year 2.
There was a 5% decrease in the number of employees from the beginning of the three years to the end of the three years.
The number of employees at the end of Year 1 was the same as the number of employees at the end of Year 3.
A group of friends shares a ride to a concert. Each friend's estimate of the time it will take to get to the concert is shown. The actual time it takes to get to the concert is 60 min. What is the percent error, to the nearest whole percent, of each friend's estimate?
Select correct answers.
Pete's percent of error was 25%.
Erin's percent of error was 6%.
Matt's percent of error was 17%.
Cherie's percent of error was 23%.
Wyatt's percent of error was 8%.
A scientist studying the growth of corn plants finds that the average height of her plants increases from 14 1/2 in to 20 3/10 in during a one-week period. To the nearest whole percent, what is the percent increase in the average height of the corn plants during this period?
29%
40%
47%
71%
A bike is on sale for 30% off the original price of $120. What is the sale price of the bike?
$90
$36
$84
$75
Last year, 72 girls signed up for the seventh-grade volleyball team. This year, 63 girls signed up. What is the percent decrease in the number of girls signing up for volleyball from last year to this year?
9%
87.5%
14.3%
12.5%
A restaurant manager keeps track of how many customers were served each week for one month. During week 1, the restaurant served 840 customers. The table shows the percent of change from one week to the next week. Determine the true statements.
The same number of customers were served in Week 4 and Week 2.
There were 1050 customers served in Week 2.
The same number of customers were served in Week 3 and Week 1.
The greatest number of customers was served during Week 4.
There was a 25% increase in customers served from Week 1 to Week 4.
A geologist studying the depth of water in a mountain lake finds that it has changed from 8,300 ft to 8,881 ft over a period of two years. What was the percent increase in the depth of the lake during the two-year period, to the nearest tenth of a percent?
6.5%
7.0%
9.3%
14.0%
Five students are guessing how many marbles are in the jar. Their guesses are shown. There are actually 132 marbles in the jar. Determine which percent's of error are correct.
Jesse's is 9%.
Margie's is 6%.
Pietro's is 26%.
Susana's is 13%.
Raul's is 14%.
Marty deposited $514 into a savings account four years ago. No other deposits and no withdrawals from the account have been made. At the end of the four-year period, the balance in the account has increased by 8%. What is the balance in Marty's account at the end of the four-year period?
$41.12
$411.20
$555.12
$925.20
A track coach wants to find out how many miles middle school and high school students run during the summer. Which approach will result in a sample that is representative of the population of middle and high school students?
Survey every third student from a directory of middle school and high school students.
Survey every student in the coach's homeroom.
Survey every tenth student from a directory of students who run track in middle school and high school.
Survey every student who is interested in joining the team.
There are 256 students who attend after-school activities at Hill Middle School. A random sample of 50 of these students are surveyed on which specific activities they prefer. The survey data is shown in the table. What is a reasonable prediction of the number of all students who would prefer to read in the library?
62
100
10
51
A store owner in a shopping mall is deciding which new merchandise might help her attract new customers. She will use a survey to help her decide. Which is the most representative sample of the population of mall visitors?
Every person making a purchase at the store will receive a link to an online survey.
Select every 5th person on the mall's email list by emailing a list of questions.
Select every 10th person entering the mall and ask survey questions in person.
Ask all mall customers she sees on one Saturday for 7 hours.
A biology teacher wants to know if the amount of time spend on homework affects students' grades. She has a total of 120 students in her classes. She will survey a sample of students. Which approaches will result in a representative sample of all the teacher's biology classes?
Survey one girl from each row of desks in all of her classes.
Survey every fourth student entering each of her biology classes.
Survey every third student in each class who also plays sports.
Survey 20 students whose names are randomly picked from her class lists.
Visitors who tour a factory that makes Middle Eastern desserts are given five different desserts to taste. After 32 students tour the factory on a field trip, they are asked which dessert they like the best. The data are shown in the table. The tour guide says the data show that about twice as many people who buy their desserts will prefer Knafeh to Mamoul.
Why is this conclusion not reasonable?
The factory may make more desserts than the 5 tasted.
Since all those surveyed were students, all buyers did not have an equal chance of being selected.
7 is more than twice as many as 3.
An athletic director wants to add two new sports at the middle school. He will use a survey to help decide which sports to add. If people are randomly selected, which group is most likely to give him a representative sample of the school population for his survey?
any student who already plays a sport
girls and boys in the seventh grade
every tenth boy who enters the school through the main entrance
any students whose names are chosen from the school directory
The manager of a local movie theater wants to use a survey to learn whether his customers prefer comedy or action movies. Determine whether each sample is likely to represent the population of movie theater customers.
Choose one fourth of customers' names out of a hat without looking.
Choose every customer who comes in on Monday.
Choose every tenth female customer.
Choose every customer who attends a comedy movie.
A community group wants to determine its citizens' support for a tax increase to pay for building a new park. Which sample is likely to be most representative of the population?
one hundred people selected at random from a list of registered voters
every odd-numbered house within three blocks of the proposed park
a random sample of fifty people walking into the local garden center
every fifteenth person on a list of names of community residents
The owner of a deli is deciding which new sandwich to add to her lunch menu. She surveys 25 lunch customers by randomly selecting five customers on each of five days during one week. The data are shown in the table. Based on the data, the owner concludes that about three times as many of her customers will prefer Israeli schnitzel sandwiches to pastrami sandwiches. Select the reasons for this conclusion.
The sample is representative of the population.
All customers had an equal chance of being surveyed.
4 x 3 = 12 which is close to 13
She surveyed all customers over a five day period.
A scientist is studying three types of fish on a random summer day and asks people fishing at a lake how many of each of the three types of fish they caught. In all, she records 211 lake trout, 189 smallmouth bass, and 21 pike caught that day. The scientist concludes that pike represent about 5% of the fish in the lake. Which is the most likely reason why the scientist's conclusion could be flawed?
The number of pike caught was not exactly 5% of the total of the three types caught.
There may have been more representative data collected on a different day.
There may have been more than three types of fish that were caught in the lake.
The number of pike caught is too small a number from which to draw a conclusion.
