分析:(1)、(3)根據(jù)小數(shù)的乘除法進行計算即可得到答案;
(2)可以用68.04分別除以0.21與3.6結果不變;
(4)、(5)按照小數(shù)的四則混合運算進行解答即可得到答案;
(6)利用加法結合律,可先計算0.01+3.99,再與0.486相加即可;
(7)利用乘法交換律,交換11與8的位置,然后再按照小數(shù)乘法進行計算比較簡便;
(8)一個數(shù)連續(xù)減去若干個數(shù)等于這個數(shù)減去若干個數(shù)的和,結果不變;
(9)一個數(shù)連續(xù)除以若干個數(shù),可用這個數(shù)除以若干個數(shù)的積,結果不變;
(10)可將2.4改寫成0.8乘以3,然則再用5.6分別除以0.8與3,最后結果不變.
解答:解:(1)6.25÷0.25×0.6
=25×0.6,
=15;
(2)68.04÷(0.21×3.6)
=68.04÷0.21÷3.6,
=324÷3.6,
=90;
(3)2.02×(1.027÷0.26)
=2.02×3.95,
=7.979;
(4)12.8-10.8÷4.5
=12.8-2.4,
=10.4;
(5)2.7÷0.75+76.4
=3.6+76.4,
=80;
(6)0.486+0.01+3.99
=0.486+(0.01+3.99),
=0.486+4,
=4.486;
(7)1.25×11×4×0.8
=1.25×0.8×4×11,
=1×4×11,
=4×11,
=44;
(8)19.75-6.45-3.55
=19.75-(6.45+3.55),
=19.75-10,
=9.75;
(9)90÷25÷4
=90÷(25×4),
=90÷100,
=0.9;
(10)5.6÷2.4
=5.6÷(0.8×3),
=5.6÷0.8÷3,
=7÷3,
≈2.33.
點評:此題主要考查的是小數(shù)四則混合運算及小數(shù)的簡便運算.