b, 53.39 + 47.39 - 53.21 - 47.21
= 39( 53 + 47) - 21 53 + 47)
= 39.100 - 21.100
= 100(39 - 21)
= 100. 18
= 1800
bấm cho mình đúng nha ^_^
a)=78.(31+24+17)+22.72
=72.(78+22)
=72.100
=7200
b)=39.(53+47)-21.(53+47)
=100.(39-21)
=100.18
=1800
Tính nhanh
a) 78*31+78*24+78*17+22*72
b) 53*39 +47*39-53*21-47*21
a) 78.31 + 78.24 + 78.17 + 22.72
= 78.(31+24+17) + 22.72
= 78.72 + 22.72
= 72.(78+22)
= 72.100
= 7200
b) 53. 39 + 47.39 - 53.21 - 47.21
= 39.(53+47) - 21.(53+47)
= 39.100 - 21.100
= 3900-2100
= 1800
=>>>> giúp mình nha <<<<=
