PSLE
Ivan packed 234 scones into large and small boxes. He filled each large box with 12 scones and each small box with 6 scones. All the boxes were full and no scones were left over. What was the least number of boxes used by Ivan?
To have the least number of boxes, Ivan had to use as many as large boxes as possible.

If Ivan used only large boxes,
number of large boxes used
= 234 ÷ 12
= 19 r 6 (x) There should be no remaining scones left.

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

If Ivan used 18 large boxes,
number of scones to be packed in small boxes
= 234 - (18 x 12)
= 234 - 216
= 18

Number of small boxes needed to pack 18 scones
= 18 ÷ 6
= 3 (✓) There is no remaining scones left.

Least number of boxes that Ivan used
= 18 + 3
= 21

Answer(s): 21