用一只平底锅煎饼，每次只能同时煎2张饼，每张饼两面都要煎，煎一面要2分钟．煎5张饼至少需要几分钟？怎样煎？如果要煎20张饼，至少需要几分钟？
直接写出得数． 1﹣=+=﹣=+=+=
计算下面各题，能用简便方法的要用简便方法计算.++++ 1﹣+﹣﹣．
看谁算的又对又快．+=+=﹣= 2﹣=+=+=
直接写得数．+=﹣= 1﹣=﹣0.25= 6+=+=+=﹣= 1﹣﹣=++=．
口算：+=﹣=+3= 2.6﹣1= 5﹣=﹣=+=﹣= 2﹣﹣=+﹣= 1﹣（+）=+++=
=
+
=
﹣
=
+
=
+
=
+
+
+
+
1﹣
+
﹣
﹣
．
+
+
=
﹣
= 2﹣
=
+
=
+
=
+
=
﹣
= 1﹣
=
﹣0.25= 6+
+
=
+
=
﹣
= 1﹣
﹣
=
+
+
=．
+
=
﹣
+3= 2.6﹣1
=
=
﹣
=
+
=
﹣
=
﹣
=
﹣
= 1
﹣（
）=
+
+
+
=
粤公网安备 44130202000953号