First, oral calculation:
25×2= 125×2= 4×25= 25×8= 4× 125= 75×4= 25×5= 125×8=
Second, it is easy to calculate.
3.78×4-6. 13 (0. 18+2.4)×3.6 3.9×(4. 1+2.9)
(4+0.4)×0.25 8×7× 1.25 (4.8-3.2)× 12.5
12. 1- 2. 1× 1.2 36×2.7+3.36×7.3 13.9×5.2-3.9×5.2
2.5×9.78×0.4 38×79+79×6 1+79 0.38× 10 1
0.58×99+5.8×0. 1 5.6× 132-3.2×56 6.2÷2.5÷0.2
4.38× 10 1-4.38 3.2× 1.25×25 3.25× 1. 1
Third, solve the equation:
4a- 18×2 = 20(n-3)÷2 = 7.5 2.5× 16-8x = 12
x+6 = 15 5+x = 25 x- 15 = 40
x × 5= 40 6x=54 x ÷ 6 =9
2x+0.7 = 2.5 0.5+4x = 4.5 5x- 1.5 = 4
x × 0.5= 4 6x=5.4 0.9x ÷ 6 =9
18.6 b-5.7b = 2.58 4m+m = 80 23.4y-3.4y = 3.4
2.2y- 1.4y = 5.6 z÷4.5 = 202.5 5x- 13 = 12
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