Question

tính nhanh 

a) 21 . 78 + 21 . 23 -21

b) 57 . 64 - 57 .3 + 39.57

c) 47.29 - 13 .29 - 24.29

d) 12.53  + 53 .172 - 53. 84

e) 24.42 - 35 .24 - 24.7

Answer 1

a, \(=21.\left(78+23-1\right)=21.100=2100\)

b, \(=57.\left(64-3+39\right)=57.100=5700\)

c, \(=29.\left(47-13-24\right)=29.10=290\)

d, \(=53.\left(12+172-84\right)=53.100=5300\)

e, \(24.\left(42-35-7\right)=24.0=0\)

Answer 2

a, 

b, 

c, 

d, 

e,