| 看谁计算又对又快 95-48= | 80×7= | 49×4≈ |
| 200×5= | 650+480= | 213×6≈ |
| 58÷6= | 999×0= | - = |
+ = | - = | 1- = |
| 95-48=47, | 80×7=560, | 49×4≈200, |
| 200×5=1000, | 650+480=1130, | 213×6≈1200, |
58÷6= , | 999×0=0, | - = , |
+ = , | - =0, | 1- = . |
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.分析:49×4把49看成50估算;213×6把213看成200估算;其它题目按照运算法则直接运算求解.
点评:再乘法的估算时常常把因数看成它接近的整十、整百、整千的数再求积.
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