Question 8: 3. Square of14× (2 ÷ 2 )× 0.25

=3. 14× 1×0.25

=0.785 cubic meters

35-0.785=34.2 15 (m3)

A: At present, 34.2 cubic meters of earth and stone are used.

Question10: 81÷ 4.5 =18 (square decimeter)

18×3=54 (cubic decimeter)

Its volume is 54 cubic decimeters.

Question 1 1: 10÷2=5 (cm)

8÷2=4 cm

3. 14×(5 squared -4 squared)

=3. 14×(25- 16)

=3. 14×9

=28.26 square centimeters

28.26×80=2260.8 (cubic centimeter)

A: It uses 2260.8 cubic centimeters of steel.

Wish: learning progress!