Tính nhanh: a,37.21+37.52+83.25+83.38 b,(3+5+7+…+99).(5252.48-4848.52) c,(2020.2021-1011):(1009+2020.2020)

Đáp án

a,`37.21+37.52+83.25+83.38` 

`= 37.(21+52) + 83.(25 + 38)`

`= 37. 73 + 83.63`

`= 37.(63+10)+ 83.63`

`= 370+ 63.37 + 83.63`

`= 370 + 63.(37+83)`

`= 370 + 7560`

`= 7930`

b,`(3+5+7+…+99).(5252.48-4848.52)`

`=(3+5+7+…+99).(52.101.48 – 48.101.52)`

`= (3+5+7+…+99).0 `

`=0`

c,`(2020.2021-1011)/(1009+2020.2020)`

`=(2020.(2020+1) – 1011)/(1009 + 2020.2020)`

`=( 2020.2020 + 2020 – 1011)/(1009+ 2020.2020)`

`=(2020.2020+1009)/(1009+2020.2020)`

`=1`