2, ( 1) 12 4

(2)3/4 0.7 1

(3) 12

(4) Rectangular circle

(5)4 24

3. Simple calculation

3.8×2.5×0.4 0.5× 12.5×8×0.2

=3.8×(2.5×0.4) =(0.5×0.2)×( 12.5×8)

=3.8× 1 = 0. 1× 100

=3.8 = 10

Step 4 solve the problem

( 1)3.8× 180。 Leather; 3.6= 190 (pieces) a: omitted

(2)0. 16×75= 12 (kg)

My weight is □ kg on the earth and 0. 16*□ = (kg) on the moon.

(3) Find the area first:10× 4+10×1.6&; Leather; 2=48 (square meters)

Weight: 0. 15 × 4 8= 7.2 (kg)

A: Omit.

Use your head:

Please draw a schematic diagram. Cut into 64 pieces, that is, the length, width and height are divided into 4 parts.

There are eight small cubes, and three faces are painted black at the vertices;

The two blackened faces are at the side length position (except the vertex), with two faces on each side and 12 faces *** 24.

A face painted black is in the middle of each face. There are 4 faces on each face and 24 faces on 6 faces.

Colorless 64-8-24-24=8 (piece)