PSLE
Daniel packed 350 cookies into large and small boxes. He filled each large box with 16 cookies and each small box with 10 cookies. All the boxes were full and no cookies were left over. What was the least number of boxes used by Daniel?
To have the least number of boxes, Daniel had to use as many as large boxes as possible.

If Daniel used only large boxes,
number of large boxes used
= 350 ÷ 16
= 21 r 14 (x) There should be no remaining cookies left.

If 21 large boxes are used, there are 14 cookies left, Daniel had to use less large boxes so that the rest of the cookies were packed in small boxes.

If Daniel used 20 large boxes,
number of cookies to be packed in small boxes
= 350 - (20 x 16)
= 350 - 320
= 30

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

Least number of boxes that Daniel used
= 20 + 3
= 23

Answer(s): 23