Question

8乘(72乘25)全部用简便方法计算 0.25乘(0.4加8) 45乘(9分之2加15分之7减5分之

Answer 1

第一题

8 X ( 72 X 25 )

= 72 X 2 X 4 X 25

= 144 X 100

= 14400

第二题

0.25 X ( 0.4 + 8 )

= 0.25 X 4 X ( 2 + 0.1)

= 1 X 2.1

= 2.1

第三题

45 X ( 2/9 + 7/15 - 1/5 )

= 45X2 /9 + 45X7 /15 - 45/5

= 5X2 + 3X7 - 9

= 10 - 9 + 21

= 22

第四题

28.4 - ( 8.4 + 5/9 )

= 28.4 - 8.4 - 5/9

= 20 - 5/9

= 19+ 4/9

第五题

( 19+ 15/16 ) X 8

= ( 20 - 1/16 ) X 8

= 20 X 8 - 8 /16

= 160 - 1/2

= 159.5

第六题

16.5 - 3.43 - 2.57

= 16.5 - ( 3.43 + 2.57 )

= 16.5 - 6

= 10.5