Question

直接寫(xiě)得數(shù)． 400×3=	2 9 + 5 9 =	65-7=	5×60=
720-80=	2 6 + 4 6 =	72÷8=	1- 3 7 =
299×4≈	103×5≈	800×7=	5 8 - 2 8 =

Answer 1

分析：根據(jù)整數(shù)加減乘除法和分?jǐn)?shù)加減法的計(jì)算方法進(jìn)行計(jì)算．

解答：解：

400×3=1200	2 9 + 5 9 = 7 9	65-7=58	5×60=300
720-80=640	2 6 + 4 6 =1	72÷8=9	1- 3 7 = 4 7
299×4≈1200	103×5≈500	800×7=5600	5 8 - 2 8 = 3 8

點(diǎn)評(píng)：口算時(shí)，注意運(yùn)算符號(hào)和數(shù)據(jù)，然后再進(jìn)一步計(jì)算．