PSLE
Paul packed 488 scones into large and small boxes. He filled each large box with 18 scones and each small box with 10 scones. All the boxes were full and no scones were left over. What was the least number of boxes used by Paul?
To have the least number of boxes, Paul had to use as many as large boxes as possible.

If Paul used only large boxes,
number of large boxes used
= 488 ÷ 18
= 27 r 2 (x) There should be no remaining scones left.

If 27 large boxes are used, there are 2 scones left, Paul had to use less large boxes so that the rest of the scones were packed in small boxes.

If Paul used 26 large boxes,
number of scones to be packed in small boxes
= 488 - (26 x 18)
= 488 - 468
= 20

Number of small boxes needed to pack 20 scones
= 20 ÷ 10
= 2 (✓) There is no remaining scones left.

Least number of boxes that Paul used
= 26 + 2
= 28

Answer(s): 28