Tính nhanh 3/5 × 6/8 + 3/5 × 2/8. 4/3 × 3/4 × 15 Tìm x X÷ 1/2 = 2/5 + 3/15.

3/5 × 6/8 + 3/5 × 2/8.

= 3/5 xx (6/8+2/8)

= 3/5 xx 1

= 3/5
——————————

4/3 × 3/4 × 15.

= (4/3xx3/4)xx15

= 1 xx 15

= 15

2, Tìm x :

x : 1/2 = 2/5 + 3/15.

x : 1/2 = 3/5

x = 3/5 xx 1/2

x = 3/10

——————————

x : 4/7 = 5/9 × 3/5.

x : 3/7 = 15/45

x = 15/45 xx 3/7

x = 1/7

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