Giải thích các bước giải:
Bài 5: tính nhanh
a, -524.[23 + (-45)]+524.(-45 + 123)
= 524.[-23 + 45]+524.(-45 + 123)
= 524.(-23+45-45+123)
= 524. 100
= 52400
b, 47.69-31.(-47)
= 47.69+31.47
= 47.(69+31)
= 47.100
= 4700
c, 16.(38-2) - 38.(16 - 1)
= 16.38-16.2-38.16-38.1
= (16.38-38.16)+(-16.2-38.1)
= 0-70
= -70
d, (-41).(59+2)+59.(41-2)
= -41.59+(-41).2+59.41-59.2
= (-41.59+59.41)+(-41.2-59.2)
= 0+2.(-41-59)
= 2.(-100)
= -200
e, 125.(-8).(-25).9.9.100.0:3
= -100.(-25).0
= 0
f, (27.99 + 99.35):31 : 2
= [99.(27+35)]:31:2
= [99.62] : 31 : 2
= 6138 : 31 : 2
= 198 : 2
= 99
g, (76.34 - 19.64):(38.9)
= [76.34 - 19.(30+34)]:342
= [ 76.34-19.30+19.34]: 342
= [ 34.(76+19)-19.30] : 342
= [ 34.19.5 - 19. 30] : 342
= [ 19.170-19.30] : 342
= [19.(170-30)] : 342
= 19.140 : 342
= 2660 : 342
= 70/9