题目内容
51
÷
+71
÷
+91
÷
．
| 2 |
| 3 |
| 5 |
| 3 |
| 3 |
| 4 |
| 7 |
| 4 |
| 4 |
| 5 |
| 9 |
| 5 |
分析：把被除数变成一个整数与一个假分数的和，将除法转化为乘法后即可简算．
解答：解：51
÷
+71
÷
+91
÷
=（50+
）×
+（70+
）×
+（90+
）×
=50×
+
×
+70×
+
×
+90×
+
×
=30+1+40+1+50+1
=123．
| 2 |
| 3 |
| 5 |
| 3 |
| 3 |
| 4 |
| 7 |
| 4 |
| 4 |
| 5 |
| 9 |
| 5 |
=（50+
| 5 |
| 3 |
| 3 |
| 5 |
| 7 |
| 4 |
| 4 |
| 7 |
| 9 |
| 5 |
| 5 |
| 9 |
=50×
| 3 |
| 5 |
| 5 |
| 3 |
| 3 |
| 5 |
| 4 |
| 7 |
| 7 |
| 4 |
| 4 |
| 7 |
| 5 |
| 9 |
| 9 |
| 5 |
| 5 |
| 9 |
=30+1+40+1+50+1
=123．
点评：考查了运算定律与简便运算，四则混合运算．注意运算顺序和运算法则，灵活运用所学的运算律简便计算．
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