6.3×0.72的積是________位小數(shù);6.8×2.134的積是________位小數(shù).
三 四
分析:(1)6.3末尾數(shù)是3,0.72末尾數(shù)2,3×2=6,那么6.3×0.72的積的小數(shù)位數(shù)是這兩個小數(shù)的小數(shù)位數(shù)和;
(2)6.8末尾數(shù)是8,2.134末尾數(shù)4,8×4=32,那么6.8×2.134的積的小數(shù)位數(shù)是這兩個小數(shù)的小數(shù)位數(shù)和.
解答:根據(jù)題意可得:
(1)6.3是一位小數(shù),0.72是兩位小數(shù);
3×2=6;
1+2=3;
所以,6.3×0.72的積是三位小數(shù);
(2)6.8是一位小數(shù),2.134是三位小數(shù);
8×4=32;
1+3=4;
所以,6.8×2.134的積是四位小數(shù).
故答案為:三,四.
點評:兩個小數(shù)相乘,如果兩個小數(shù)的末尾數(shù)相乘的末尾不是0,它們的乘積的小數(shù)位數(shù)就是這兩個小數(shù)位數(shù)的和.