一本笔记本3.5元，一支钢笔2.5元．（1）淘气买了1本笔记本和a支钢笔，共付 元．（用含字母的式子表示）（2）当a=5时，淘气要付多少钱？（3）淘气共付了11元，他买了几支钢笔？
口算56×= 2﹣= += 6×= 0.25×4= 57×=÷= 1÷= 21÷= ÷= 1÷= 0÷=
计算下面各题．×21× ÷5× ÷÷÷÷24 ×÷8．
计算．×9= ×0= 0÷= ÷=12×= ×= ÷= ÷=
直接写得数×= ÷5= ×12= ×= ÷=÷= ×= 1÷= = 45×=÷2= ÷= ×= ÷= ×0=×= 1﹣= ÷= ×= 15÷=
口算×6= += ×= ×6= ÷=÷= 1﹣= ﹣= ×4= ÷=
= 2﹣
= 
+
= 6×
= 0.25×4= 57×
=
÷
= 1÷
= 21÷
= 
÷
= 1÷
= 0÷
=
×21×
÷5×
÷
÷
÷
÷24 
×
÷8．
×9= 
×0= 0÷
= 
÷
=
×
= 
÷
= 
÷
=
×
= 
÷5= 
×12= 
×
= 
÷
÷
= 
×
= 1÷
= 
= 45×
=
÷2= 
÷
= 
×
= 
= 
×0=
×
= 1﹣
= 
÷
= 
×
= 15÷
=
×6= 
+
= 
×
= 
×6= 
÷
=
÷
= 1﹣
= 
﹣
= 
×4= 
÷
=
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