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)

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1. 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`

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