求數(shù)(三年級(jí)奧數(shù)題及答案)

字號(hào):

求數(shù)
    (1)4×4× …… ×4(25個(gè)4)積的個(gè)位數(shù)是幾?
    (2)20個(gè)2相乘,積末尾數(shù)字是幾?
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    解答:(1)按照乘數(shù)的個(gè)數(shù),積的末位數(shù)字的規(guī)律是:4,6,4,6,4,6,……奇數(shù)個(gè)4相乘得數(shù)的末尾數(shù)字是4,偶數(shù)個(gè)4相乘得數(shù)的末尾數(shù)是6,25是奇數(shù),25個(gè)4相乘,積的末尾數(shù)字是4.
    (2)按照乘數(shù)的個(gè)數(shù),末尾數(shù)字的規(guī)律是2,4,8,6,2,4,8,6……4個(gè)一組20÷4=5所以20個(gè)2相乘,積末尾數(shù)字是6.