可汗学院
1.Dalia makes a cranberry apple punch that contains 20% real juice by mixing x gallons of a cranberry drink with y gallons of an apple drink. The cranberry drink contains 40% real juice and the apple drink contains 10% real juice. Which of the following equations represents the relationship between x and y?
A.0.4x+0.1y=20
B.0.4x+0.1y=x+y
C.0.20(x+y)=x+y
D.0.2(x+y)=0.4x+0.1y
Correct answer: D
2.Gary learned that the value of his car depreciates by 15% per year. Which of the following functions best describes the value of his car the year after the car is worth m dollars?
A.f(m)=0.15m
B.f(m)=0.85m
C.f(m)=1−0.15m
D.f(m)=1−0.85m
Correct answer: B
3.Javier has a cell phone plan that allows him to use up to 4 gigabyte (GB) of data per month. Streaming videos is the only action he does on his phone which uses up this data. Each time he streams a video, the amount of gigabytes of his phone's data plan decreases. Specifically, his cell phone company estimates that approximately 0.12 GB of data are used for every 30minutes of video streaming. If Javier has spent m minutes this month streaming videos, which of the following best approximates the amount of data, d, he has remaining on his plan?
A.d=4−0.12m
B.d=4+0.12m
C.d=4−0.004m
D.d=4+0.004m
Correct answer: C
4.Li Jing has already read of her 384 page book. She figures that she reads at a constant rate and can read about 45 pages in 11 hour. If mm is the amount of time, in minutes, that Li Jing has spent reading the final of the book, which of the following best approximates the number of pages, p, that she has left?
A.p=128−45m
B.p=256−45m
C.p=128−43m
D.p=256−43m
Correct answer: D
5.Between 2008 and 2012, the revenue obtained from digital music album downloads, r, in millions of dollars, in the United States increased by approximately 132 million dollars per year. In 2010, the digital music revenue in the U.S. was about 872 million dollars. If t represents years since 2008, which of the following best models the situation for ?
A.r(t)=132t
B.r(t)=132t+608
C.r(t)=132t+872
D.r(t)=132t+1136
Correct answer: B
6.David's vehicle has a 21 gallon gas tank. If he drives only on highways, he can go about 525miles on one tank of gas. If he drives only in the city, he can go about 378 miles on one tank of gas. David drove 455 miles on his last tank of gas. If x is the amount of gallons used on highway driving and y is the gallons used on city driving, which of the following best models the relationship between x and y in this situation?
A.25x+18y=21
B.25x+18y=455
C.525x+378y=21
D.525x+378y=455
Correct answer: B
7.Mikayla is a waitress who makes a guaranteed $50 per day in addition to tips of 20% of all her customer receipts, t. She works six days per week. Which of the following functions best represents the amount of money that Mikayla makes in one week?
A.f(t)=50+20t
B.f(t)=300+20t
C.f(t)=50+0.2t
D.f(t)=300+0.2t
Correct answer:
