可汗学院
1.Maria burns about 600 calories per hour jogging and about 450 calories per hour biking. If Maria spends x hours per day biking, and 4/5 as much time jogging, which of the following functions best models the amount of calories, C, that Maria burns in one day from jogging and biking?
A.C(x)=840x
B.C(x)=930x
C.C(x)=960x
D.C(x)=1050x
Correct answer: B
2.Mikayla walked nine miles in three hours. She walked f miles during the first hour and 2/3 of the remaining distance during the second hour. Which of the following functions best represents the number of miles in the third hour, t, she had to walk in terms of the number of miles she walked in the first hour, f ?
A.t=3
B.t=3−1f/3
C.t=3+2f/3
D.t=3+f
Correct answer: B
图 289
4.Sterling silver is an alloy of silver that is 92.5% pure silver. If x grams of sterling silver are mixed with y grams of an 88% silver alloy to produce a 91% silver alloy, which of the following equations correctly relates x and y?
A.0.075x+.12y=0
B.0.015x−0.03y=0
C.0.925x+0.88y=91
D.0.925x+0.88y=0.91xy
5.A roller coaster is currently traveling at a speed of 49 miles per hour (mph). The coaster’s speed will increase at a constant rate of 17mph every 2 seconds until the coaster reaches its top speed 5 seconds from now. If t≤5, which function best represents the roller coaster’s speed, in miles per hour, t seconds from now?
A.f(t)=49+8.5t
B.f(t)=49+17t
C.f(t)=49t+9.8t
D.f(t)=49t+17t
Correct answer: A
6.Gustav is starting a special sprinting regimen in outdoor track. The regimen suggests sprinting for a certain number of seconds, s, at first. The second time he sprints, he should run 150 more seconds than the first time. For the third time, the regimen suggests sprinting twice the number of seconds as the first time. Finally, the regimen suggests an 80-second sprint. Which of the following functions can be used to find the total number of seconds, t, suggested by the entire sprinting regimen?
A.t=s+230
B.t=2s+230
C.t=5s/2+230
D.t=4s+230
Correct answer: D
7.In 2007, approximately 50% of the world's population lived in rural (defined as non-urban) areas. From 2005 to 2013, the percent of the world's population living in rural areas decreased by about 0.5 percentage points per year. If t represents years since 2005, which of the following equations best models the percent of the world's population living in rural areas, r, from 2005 to 2013?
A.r−50=−0.5(t−2)
B.r−50=−0.5(t−7)
C.r−2=−0.5(t−50)
D.r−7=−0.5(t−50)
Correct answer: A
8.Maria burns about 600 calories per hour jogging and about 450 calories per hour biking. If Maria spends x hours per day biking, and 4/5 as much time jogging, which of the following functions best models the amount of calories, C, that Maria burns in one day from jogging and biking?
A.C(x)=840x
B.C(x)=930x
C.C(x)=960x
D.C(x)=1050x
Correct answer: B
