Helium: 660× 78/2 1+78 = 520 (m3)

2. The solution 1 220 ÷ 12 = 20 (ml) 20× 1 = 20 (ml) 20× 9 = 180 (ml).

Solution 2 200×110 = 20 (ml) 200× 9/ 10 = 180 (ml).

3. Solution 1 7+ 1 = 8 (name) 56× 1/8 = 7 (name) 56× 7/8 = 49 (name)

Solution 2 56 ÷ (1+7) = 7 (name) 1× 7 = 7 (name) 7×7 =49 (name)

4. Solution12+3+5 =10 20× 2/10 = 4 (ton) 20× 3/ 10 = 6 (ton).

20× 5/ 10 = 10 (ton)

Solution 2 20 ÷ (2+3+5) = 2 (ton) 2× 2 = 4 (ton) 2×3=6 (ton)

2× 5 = 10 (ton)

5. Solution1120÷ 4 = 30 (cm) 3+2+1= 6 30× 3/6 =15 (cm) 30× 2/6 =/kloc-0.

30×1/6 = 5cm

Solution 2120 ÷ 4 = 30 (cm) 3+2+1= 6 30 ÷ 6 = 5 (cm).

5×3= 15 (cm) 5×2= 10 (cm) 5× 1=5 (cm)

6. Method 1. 800× 2/5 = 320 (square meter) 800-320 = 480 (square meter).

4 80×1/2+1=160 (m2) 480×2/2+ 1=320 (m2)

Method two. 480÷(2+ 1)= 160(m2) 160× 1 = 160(m2) 160×2 = 320(m2)。