analyse

According to the characteristics of a cube, the lengths of 12 sides are all equal, and the areas of 6 faces are all equal; To find out how much iron sheet should be used to make this tin box, it is necessary to find out its surface area. The formula of cubic surface area is: s=6a? Because it is a cubic iron box without a cover, the surface area of 1 iron box =5a? The volume formula is: v=a? ; Solve according to the formula.

explain

Solution:

1 Surface area of uncovered iron box

=0.8×0.8×8

=0.64×5

=3.2 square meters

Making 100 uncovered iron boxes requires iron sheet area.

= 100×3.2

=320 square meters

The volume of each tin box

=0.8×0.8×0.8

=0.5 12 (m3)

100 volume of iron box

= 100×0.5 12

=5 1.2 (m3)

Answer: These iron boxes should use at least 320 square meters of iron, and the volume of each iron box is 0.5 12 cubic meter.

2、

analyse

Considering that the number of TV sets is 1, we can see that the washing machines sold are 8÷ 17=8/ 17.

explain

Solution:

The washing machine sold is 817 = 8/17 of the TV set.

Answer: The washing machine sold is 8/ 17 of the TV set.

3、

analyse

The volume of the steel ball = the volume of the rising part of the water surface of the cuboid container

explain

Solution:

Steel ball volume

= the volume of the rising part of the water surface of a cuboid container

= Length× Width× (current height-original height)

= 12x 10x(9-6)

=360 (cubic centimeter)

The volume of steel balls is 360 cubic centimeters.