1. tính bằng cách hợp lí :
a. 5 . 125 . 2 . 41 . 8 = c. 8 . 12 . 125 . 2 =
b. 25 . 7 . 10 . 4 = d. 4 . 36. 25 . 50 =
2. tính nhanh :
a. 37 . 7 + 80 . 3 + 43 .7 b. 113 . 38 + 113 . 62 + 87 . 62 + 87 . 38
c. 123 . 456 + 456 . 321 - 256 . 444 d. 43 . 37 + 93 . 43 + 57 . 61 + 69 . 57
a) (5.2).(125.8).41= 10.1000.41=410000
a) 5 . 125 . 2 . 41 . 8
=(5.2).(125.8).41
= 10 . 1000 . 41
= 10000 . 41
= 410000
b) 25 . 7 . 10 . 4
=(25.4).(7.10)
= 100 . 70
= 7000
c) 8 . 12 . 125 . 2
= (8.125).(12.2)
= 1000 . 24
= 24
d) 4 . 36 . 25 . 50
=(4.25).(36.50)
= 100 . 180
= 18000
2.
a) 37 . 7 + 80 . 3 + 43 . 7
= 7. (37 + 43) + 80 . 3
= 7 . 80 + 240
= 560 + 240
= 800