5400 103 180 6

900 960 3 800

Second, use recursive equation to calculate.

(420÷28+ 12)×5= 135

500-(320+320÷4)= 100

480÷80+42× 17=720

Third, solve the problem.

1, 160÷30=5 (architecture) ... 10 (Zhang)

Answer: You can post five math buildings, and there is 10 left.

2,400,000 ÷ 4,000 =1000 (tree)

A: 1 0,000 big trees with wide bowls need to be cut down.

3. (1620-140× 3) ÷150 = 8 (days)

A: It will take another eight days.

4、∠2= 180 -2∠2= 180 - 120 =60

Answer: ∠2 is 60 times.

Fourth, use your head.

192÷ 12= 16

2880÷ 12=240

16×240=3840

A: The product of two numbers is 3840.