1.3. 15 hours =(3) hours (9) minutes.

2. Put two squares with equal area together to form a rectangle. The circumference of this rectangle is 24 cm, and the area of each square is (16) square cm.

3. The radius of the great circle is one centimeter, the diameter of the small circle is one centimeter, and the area of the small circle is (25 )% of the area of the great circle.

4. Make a cuboid with the smallest surface area by using three cuboids with a length of 3cm, a width of 2cm and a height of 1cm, and the surface area of this cuboid is (42cm2).

5. Party A and Party B can complete a batch of parts in 8 days, with one person for Party A 12 days and one person for Party B for 24 days.

Second, multiple choice questions

1.A is 50, which is 20% more than B. The formula for finding how much A is more than B is (C).

A.50 * (1+20%) b.50 * 20% c.50/(1+20%) * 20%.

2. A 2-meter-long wood cube with a width and thickness of 5% was sawed into two sections with a length of 1 meter, and the surface area was increased by (50) square decimeter.

A.20 B.5 C.25 D.40

3. Application questions.

1. For a project, it takes 8 days for Party A to do it alone, 10 days for Party B, and 9/00 of 10 days for two teams to do it at the same time?

65438+9/00 (1+1) = 4 days.

2. It takes one third of the length of a rope, that is, more than 4 meters. At this point, the remaining rope is 90 meters more than used. How long is this rope?

(90+4+4)； [( 1- 1)- 1]= 294m。

3. A car driving from A to B needs 1 in the first hour and 1 in the second hour. At this time, it is still15km away from the midpoint. How many kilometers is it between A and B?

15÷[ 1-5 1-5 1×( 1+3 1)]= 450km。

4. A truck travels 30 kilometers per hour from A to B. After the whole journey 1, a car travels 40 kilometers per hour from B to A. Three hours later, the car meets the truck. How many kilometers is it between A and B?

(40+30)×3÷( 1- 1)= 3 15km。