8、 16、24、32、40

24、48、72

24

The second big problem

8×9=72 3×5×3=45 2×5×3=30 8×9×2= 144 4×5×7= 140 2×3×2×3×2=72

3×3× 10=90

The third big problem

1 and 35 or 5 and 7 A×B 17 and 68, with a minimum of 28 and a maximum of 84.

The fourth big problem

C B

The fifth big problem

× × √

Extended space

The first small problem, 5× 8× 5 = 200 cm, 200 ÷ 40 = 5 cm, 5× 8 = 40 pieces, 200 ÷ 25 = 8 cm, at least 40 pieces should be used.

The minimum common multiple of the second item 5, 10 and 15 is 30, so there will always be simultaneous departures in at least another 30 minutes.

Mathematics wisdom garden

3× 3× 3 = 27 decimeter (18÷ 3 )× (15÷ 3 )× (12÷ 3) = 6× 5× 4 =120. The volume of each cube is 27 minutes.