Question

Tính bằng cách thuận tiện 

A) 1/3x 1/2 + 1/2 x 1/5

B) 1/3 x 1/2 - 1/5 x 1/2

Answer 1

`1/3xx 1/2 + 1/2 xx 1/5`

`=1/2 xx (1/3 +1/5)`

`= 1/2 xx ( 5/15 +3/15)`

`= 1/2 xx 8/15`

`= 8/30`

`=4/15`

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`1/3 xx 1/2 - 1/5 xx 1/2`

`= 1/2 xx (1/3 -1/5)`

`= 1/2 xx ( 5/15 -3/15)`

`=1/2 xx 2/15`

`= 2/30`

`=1/15`

Answer 2

a)

`1/3xx1/2+1/2xx1/5`

`=1/2xx(1/3+1/5)`

`=1/2xx(5/15+3/15)`

`=1/2xx8/15`

`=4/15`

b)

`1/3xx1/2-1/5xx1/2`

`=1/2xx(1/3-1/5)`

`=1/2xx(5/15-3/15)`

`=1/2xx2/15`

`=1/15`

Answer 3

a)

$1/3xx1/2+1/2xx1/5$

$=1/2xx(1/3+1/5)$

$=1/2xx(5/15+3/15)$

$=1/2xx8/15$

$=4/15$

b)

$1/3xx1/2-1/5xx1/2$

$=1/2xx(1/3-1/5)$

$=1/2xx(5/15-3/15)$

$=1/2xx2/15$

$=1/15$