PSLE
Luis packed 272 macarons into large and small boxes. He filled each large box with 14 macarons and each small box with 10 macarons. All the boxes were full and no macarons were left over. What was the least number of boxes used by Luis?
To have the least number of boxes, Luis had to use as many as large boxes as possible.

If Luis used only large boxes,
number of large boxes used
= 272 ÷ 14
= 19 r 6 (x) There should be no remaining macarons left.

If 19 large boxes are used, there are 6 macarons left, Luis had to use less large boxes so that the rest of the macarons were packed in small boxes.

If Luis used 18 large boxes,
number of macarons to be packed in small boxes
= 272 - (18 x 14)
= 272 - 252
= 20

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

Least number of boxes that Luis used
= 18 + 2
= 20

Answer(s): 20