Question

用简便方法计算，怎么算。

Answer 1

3/5+29×3/5
=3/5×（1+29）
=3/5×30
=18
3/7×21+4/7×21
=（3/7+4/7）×21
=1×21
=21
2/3×1/2+0.5
=（2/3+1）×1/2
=5/3×1/2
=5/6
3/4×2/3×5/8
=1/2×5/8
=5/16

追问

为什么第三题是加一

追答

因为：0.5本身就是1个1/2，也就是可以写成1/2×1，只不过因为任何数与1相乘都得原数，所以省略了“×1”，直接写原数。

Answer 2

3/5+29×3/5
=3/5×(1+29)
=3/5×30
=18
3/7×21+4/7×21
=21×(3/7+4/7)
=21
2/3×1/2+0.5
=(2/3+1)×1/2
=5/3×1/2
=5/6
3/4×2/3×5/8
=3/3×2/4×5/8
=1/2×5/8
=5/16

Answer 3

3/5+29×3/5
=3/5×（1+29）
=3/5×30
=18

3/7×21+4/7×21
=（3/7+4/7）×21
=1×21
=21

2/3×1/2+0.5
=（1+2/3）×1/2
=5/3×1/2
=5/6

3/4×2/3×5/8
=1/2×5/8
=5/16

追问

可以追问吗