Question

我是口算小能手． 9 10 × 8 9 =	6 7 × 3 2 =	9 8 × 3 4 =
17 20 × 5 6 =	1 8 × 1 4 =	2 5 × 5 12 =
7 8 × 8 7 =	4 5 × 5 8 =	3 10 × 5 6 =

Answer 1

分析：①②④⑥⑦⑧⑨约分计算；③⑤分子相乘的积做分子，分母相乘的积做分母．

解答：解：

9 10 × 8 9 = 4 5	6 7 × 3 2 = 9 7	9 8 × 3 4 = 27 32
17 20 × 5 6 = 17 24	1 8 × 1 4 = 1 32	2 5 × 5 12 = 1 6
7 8 × 8 7 =1	4 5 × 5 8 = 1 2	3 10 × 5 6 = 1 4

点评：此题考查了分数乘法的计算，能约分的要约分．