SAT Linear functions Practice Question 17 (Hard)

Math · AlgebraHard

Water is drained from a tank at a constant rate. Ten minutes after draining begins, the tank holds $340$ gallons, and $25$ minutes after draining begins, it holds $220$ gallons. How many minutes after draining begins will the tank be empty?

$27.5$

$42.5$

$52.5$

$55$

Show answer and explanation

Answer: C

The rate is $\frac{220 - 340}{25 - 10} = -8$ gallons per minute. At $t = 0$ the tank held $340 + 8(10) = 420$ gallons, so $V(t) = 420 - 8t$ . Setting $V(t) = 0$ gives $t = \frac{420}{8} = 52.5$ .

Choice B divides 340 by 8, which counts minutes from the 10-minute mark rather than from the start.

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