【点评】此题考查百分数的实际应用,解决此题的关键是理解第二次喝的牛奶是80%的40%.
四、计算题(共32分)
22.(8分)直接写得数.
÷
=0.375÷0.625=
×
=9﹣
=
100÷1%=×
÷
×
=5÷
=0.42=
【分析】根据小数和分数加减乘除法运算的计算法则计算即可求解.注意×
÷
×
变形为(
÷
)×(
×
)计算.
【解答】解:
÷
=
0.375÷0.625=
×
=
9﹣
=8
100÷1%=10000×
÷
×
=
5÷
=250.42=0.16
【点评】考查了小数和分数加减乘除法运算,关键是熟练掌握计算法则正确进行计算.
23.(12分)脱式计算,怎样简便就怎样算.
(+
)÷
7.8×6.9+1.2×6.9+6.9
4.5×12.5%+1.5×+1.25
÷5+
÷
+0.2.
【分析】①把除法变成乘法,再用乘法分配律计算即可;
②用乘法分配律计算即可;
③把1.25变成0.125×10,再用乘法分配律计算即可;,
④把除法变成乘法,再用乘法分配律计算即可;
【解答】解:①(+
)÷
=(+
)×
=
=
=
②7.8×6.9+1.2×6.9+6.9
=(7.8+1.2+1)×6.9
=10×6.9
=69
③4.5×12.5%+1.5×+1.25
=4.5×0.125+1.5×0.125+0.125×10
=(4.5+1.5+10)×0.125
=16×0.125
=2×(8×0.125)
=2×1
=2
④÷5+
÷
+0.2
=
=
=
=