PSLE
Oscar packed 494 wafers into large and small boxes. He filled each large box with 16 wafers and each small box with 10 wafers. All the boxes were full and no wafers were left over. What was the least number of boxes used by Oscar?
To have the least number of boxes, Oscar had to use as many as large boxes as possible.

If Oscar used only large boxes,
number of large boxes used
= 494 ÷ 16
= 30 r 14 (x) There should be no remaining wafers left.

If 30 large boxes are used, there are 14 wafers left, Oscar had to use less large boxes so that the rest of the wafers were packed in small boxes.

If Oscar used 29 large boxes,
number of wafers to be packed in small boxes
= 494 - (29 x 16)
= 494 - 464
= 30

Number of small boxes needed to pack 30 wafers
= 30 ÷ 10
= 3 (✓) There is no remaining wafers left.

Least number of boxes that Oscar used
= 29 + 3
= 32

Answer(s): 32