Question

a.Tính bằng cách thuận tiện nhất 

1. 23+23x2+23x3+23x4

2. 248x2005-2005x148

b.Tính

1. 2/3 - 5/9 x 3/4

2. 7/9 x 3/14 : 5/8

( MÌNH CẦN GẤP ĐÁP ÁN )

Answer 1

`a)`

`1)`

` 23+23xx2+23xx3+23xx4`

`= 23 xx(1+2+3+4)`

`=23 xx 10`

`=230`

`2)`

`248xx2005-2005xx148`

`= 2005xx(248-148)`

`=2005xx100`

`=200500`

`b)`

`1)`

`2/3 - 5/9 xx 3/4`

`= 2/3- 15/36`

`= 2/3-5/12`

`= 8/12-5/12`

`= 3/12=1/4`

`2)`

`7/9 xx 3/14 : 5/8`

`= 7/9 xx 3/14xx8/5`

`=(7xx3xx8)/(9xx14xx5)`

`= 168/ 630`

`=4/15`

 

Answer 2

a) 

1. \(=23\left(1+2+3+4\right)=23.10=230\)

2. \(=2005\left(248-148\right)=2005.100=200500\)

b)

1. \(\dfrac{2}{3}-\dfrac{5}{9}.\dfrac{3}{4}=\dfrac{2}{3}-\dfrac{5}{12}=\dfrac{1}{4}\)

2. \(\dfrac{7}{9}.\dfrac{3}{4}:\dfrac{5}{8}=\dfrac{7}{12}:\dfrac{5}{8}=\dfrac{14}{15}\)

Answer 3

bn tham khảo bài a (1 , 2 )