alleryStart learning →A tank fills at a steady rate. After 3 minutes it holds 46 litres, and after 8 minutes it holds 96 litres. At what rate is the tank filling?
A12 litres per minute
B10 litres per minute
C18 litres per minute
D15 litres per minute
Answer & Solution
Correct answer: B. 10 litres per minute
1. The output is the volume in litres and the input is the time in minutes.
2. The volume changes by 96 litres minus 46 litres, which is 50 litres.
3. The time changes by 8 minutes minus 3 minutes, which is 5 minutes.
4. Dividing the change in output by the change in input gives 50 litres divided by 5 minutes, which is 10 litres per minute.
5. Option A comes from dividing 96 by 8 and ignoring the 46 litres already in the tank, which is the usual trap here.
_Source: OpenStax College Algebra (CC BY 4.0), Ch 4 "Linear Functions", section 4.1 Linear Functions_
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