AlgebraEasy–MediumMeaning of a slope in context
Algebra practice question
The number of litres of paint, P, needed to cover w square metres of wall is given by P = 0.1w + 0.5. What does the number 0.1 represent in this model?
- A. The additional litres of paint needed for each additional square metre of wall.Correct
- B. The litres of paint needed when there is no wall to cover.
- C. The number of square metres one litre of paint covers.
- D. The total litres of paint needed for the whole wall.
Answer: A. The additional litres of paint needed for each additional square metre of wall.
0.1 multiplies w, so it is the change in P for each extra unit of w: every extra square metre needs 0.1 more litres.
Why the other answers are wrong
- B. The litres of paint needed when there is no wall to cover.
- That is the constant 0.5, the value of P when w = 0.
- C. The number of square metres one litre of paint covers.
- Square metres per litre would be 1/0.1 = 10, the reciprocal of the slope.
- D. The total litres of paint needed for the whole wall.
- The total depends on w; 0.1 is a rate, not a total.
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