38.15<38.1 2.8≈2.8 8.9≈9.0
- = - = + = + = 3- =
53= + = = + - =
42÷6 8 640÷8 24÷4×24
45÷916÷8×3 81÷972÷8 4×(54÷6) 18+8×2
(每个小方格的边长是1厘米)