9. There are six combinations of * * *: 3+4=7, 3+5=8, 3+6=9, 4+5=9, 4+6= 10, 5+6 =1. Because two thirds >; 1/3, so the odds of winning the prize are high if the sum is singular.

The product * * * has six combinations: 3×4= 12, 3×5= 15, 3×6= 18, 4×5=20, 4×6=24, 5×6=30. Because 1/6

10, the sum of the five cards on the left is 6×5=30, and the sum of the five cards on the right is 4×5=20.

30+20=50 (add a little in the middle), and the sum of 1 ~ 9 is 45.

So, the middle is: 50-45=5.

Comprehensive formula: 6× 5+4× 5-(1+2+3+4+5+6+7+8+9) = 5.

1 1, 7-15 ÷ 3 = 2 (cm) (15 ÷ 3 is to pour all the juice in container B into container A, and the height of the juice without ice in container A divided by 3 is the same volume, and the height of the equilateral cone is the height of the cylinder. 2 cm refers to the height of juice rising after ice cubes are put in. )

Remember: the volume of juice in the rising part is the volume of ice.

So, 3. 14×5? ×2= 157 (cubic centimeter)

12, this road is solved with the knowledge of proportion and ratio.

The first question:

Solution: Suppose my son walked x meters.

100:x=40:30

40x= 100×30

x = 3000÷ 40

x=75

My son walked 75 meters, so there is still 100-75=25 (meters) from the finish line.

The second question:

The equivalent of meeting is translated as: How many meters did my father walk from two places 25 meters apart to the meeting place?

40: 30 = 4: 3, 4+3=7. When we met, my father walked four-sevenths of 25 meters.

So my father left: 25×4/7= 100/7 (meters).