100x5-5x98-9=?

100x5-5x98-9

= 5 X (100 - 98 ) -9

= 1

100x5-5x98-9
=500-5x98-9
=500-490-9
=10-9
=1

有1個更快的方法

100x5-5x98-9
=5x(100-98)-9 (抽公因子5出黎,即5x(100x1-98x1))
=5x2-9
=10-9
=1

1"_"

1
1
1

100x5-5x98-9
=500-5x98-9
=500-490-9
=10-9
=1

答案:等於1。

100x5-5x98-9
=500-490-9
=10-9
=1

答案係1....

口訣:先乘除,後加減。
可以睇成:(100x5)-(5x98)-9
所以先做乘既部份...
STEP 1: 100x5= 500
5x98= 490
之後做減既部份...
STEP 2: (500)-(490)-9
=1

100x5-5x98-9
=500-490-9
=1

100 x 5 - 5 x 98 - 9
= 500 - 490 - 9
=1

59 lo~