Help!!!數學題１０分﹗

24 x 30 = 24 x 3 x 10 = 72 x 10

720 x 12 = 720 x 10 + 720 x 2 = 7200 + 1440 = 8640

通常心算: 24 x 3 x 10 x 10 = 7200
7200 + 720 x 2 = 8640

先用30x12因為其中一個有0所以x的時候比較快或24x30先:
如下
12 24
x30 x30
360 720

24 12
x360 x720
7200 8400
+1440 + 240
8640 8640

8640的確有快的方法,就是不告訴你們@

1)
24 x 30 x 12
= 3 x 8 x 3 x 10 x 3 x 4
= 3 x 3 x 3 x 4 x 8 x 10
= 3^3 x 4 x 80
= 27 x 4 x 80
= 8 640

2)
24 x 30 x 12
= 24 x 10 x 3 x 12
= 240 x 36
= 8 640

3)
24 x 30 x 12
= 計算機

4)
24 x 30 x 12
= 直式

first 30 X 12 X 24
=360 X 24
=8640

20x30x12 =7200

24x30x12
=2(12)x30x12
=2(12二次)30
=(144)60
=8640

24*30*12
=24*10 + 24*2 +24*30
=(240+48) 30
=8640

先將24×12,再將24×12的總數×30,就得

24
x 30
----------
720


720 x 12
=720x10+620x2
=7200+1240
=8440