Question

Mrs Sam bought 4 watermelons and 5 papayas for R45,75. If she had bought 5 watermelons and 10 papayas instead, it would cost R66. Find the cost of 12 watermelons.

Answer 1

If W and P are the unit costs of watermelons and papayas then:

4W+5P=45.75, 5W+10P=66.

So 8W+10P=91.50, 10P=91.50-8W, and we can substitute in the other equation:

5W+91.50-8W=66, 3W=91.50-66=25.50, W=25.50/3=8.50, and 12 watermelons cost 12×8.50=R102.