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Shereen Elebeidy

اکتوبر 28, 2018 23:17

A tank initially contains 7 gallons of water. A faucet is opened and water begins pouring into the tank at a rate of 1.5 gallons per minute untill the tank is full. Which of the following represents the volume v of water , in gallons, in the tank as a function of time t , in minutes, that has elapsed since the faucet was opened?
A) V(t) = 1.5+ t
B) V(t) = 8.5+ t
C) V(t) = 1.5t
D) V(t) = 1.5t -7
E) V(t) = 1.5t +7

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Arindam Mishra

اکتوبر 29, 2018 08:47
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Hey Shereen.

The answer to the question is (E).

Since the tank already had 7 gallons of water, the volume expression would be given by 'x'+7, where x is the rate of flow of water in the tank. It is given that the faucet adds 1.5 gallons of water per minute. Hence the rate of flow of water is 1.5t. This suggests that after 1 minute, the tank will have 8.5 gallons of water [ 1.5(1)+7 ] , after 2 minutes, the volume will be 10 gallons [ 1.5(2) +7] and so on.

Hope you get it.

Best of Luck. :)
Shereen Elebeidy

اکتوبر 29, 2018 11:39

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That was exactly my answer but many math teachers say that we should not count the initial 7 gal in the equation making the answer C
So I needed a confirmation from khan academy's team that it's E

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