Question

3.84×5.19的積有________位小數(shù)，37.8縮小到它的百分之一是________．

Answer 1

4    0.378
分析：根據(jù)小數(shù)乘法的計算法則：先按照整數(shù)乘法的計算法則算出積，再看兩個因數(shù)一共有幾位小數(shù)，就從積的右邊起數(shù)出幾位點上小數(shù)點．據(jù)此解答．
把37.8縮小到原來的百分之一，小數(shù)點向左移動兩位，不足兩位的用0補足；即可得解．
解答：根據(jù)小數(shù)乘法的計算法則可知：積的小數(shù)位數(shù)等于兩個因數(shù)小數(shù)位數(shù)的和．
所以，3.84×5.19的積有四位小數(shù)；
37.8縮小到它的百分之一是0.378．
故答案為：4，0.378．
點評：此題考查的目的是掌握小數(shù)乘法的計算法則，明確：積的小數(shù)位數(shù)等于兩個因數(shù)小數(shù)位數(shù)的和．
同時考查了小數(shù)點位置的移動與小數(shù)大小的變化規(guī)律：小數(shù)點右移一位，原數(shù)擴大10倍，小數(shù)點右移二位，原數(shù)擴大100倍，小數(shù)點右移三位，原數(shù)擴大1000倍；左移一位，原數(shù)縮小10倍，左移二位，原數(shù)縮小100倍，左移三位，原數(shù)縮小1000倍．