2. Tính :
a) 2/3 x 4/5 = ................................ 8/15 : 2/3 = ......................................
2/3 x 4/5 x 6/7 = ................................... 1/3 : 3/4 = ..............................
b) 2/7 x 3 = ................................... 6/7 : 3 = ...........................................
4 x 2/9 = ................................... 8/9 : 4 = ..........................................
`a)`
`2/3 xx 4/5 = (2xx4)/(3xx5)=8/15`
`8/15 : 2/3 = 8/15 xx 3/2= (8xx3)/(15xx2)=24/30=4/5`
`2/3 xx 4/5 xx 6/7 = (2xx4xx6)/(3xx5xx7)= 48/105 =16/35`
`1/3 : 3/4 =1/3 xx 4/3= 4/9`
`b`
`2/7 x 3 =(2xx3)/7=6/7`
` 6/7 : 3 = 6/7 xx 1/3= 6/21=2/7`
` 4 xx 2/9 = (4xx2)/9=8/9`
`8/9 : 4 =8/9 xx 1/4=8/36=2/9`
`2/3 xx 4/5 = ( 2 xx 4 ) /( 3 xx 5 ) = 8/15`
`2/3 xx 4/5 xx 6/7 = 8/15 xx 6/7 = 48/105 = 16/35`
`8/15 : 2/3 = 8/15 xx 3/2 = 24/30 = 12/15`
`1/3 : 3/4 = 1/3 xx 4/3 = 4/9`
`2/7 xx 3 = 6/7`
`4 xx 2/9 = 8/9`
`6/7 : 3 = 6/7 xx 1/3 = 6/21`
`8/9 : 4 = 8/9 xx 1/4 = 8/36 = 2/9`