* $43,2km/h= m/s$

$43,2km/h = 43,2 : 3600 km/s = 0,012 km/s$

$0,012 km/s = 0,012. 1000 m/s = 12 m/s$

$⇒$ $43,2km/h= 12 m/s$

* $54km/h= m/s$

$54km/h = 54 : 3600km/s = 0,015 km/s$

$0,015 km/s = 0,015 . 1000 m/s  = 15 m/s$

$⇒$ $54km/h= 15 m/s$

* $28,8km/h= m/s$

$28,8km/h = 28,8 : 3600 km/s = 0,008 km/s$

$0,008 km/s = 0,008 . 1000 m/s = 8 m/s$

$⇒$  $28,8km/h= 8 m/s$

* $18km/h= m/s$

$18 km/h = 18 : 3600 km/s = 0,005 km/s$

$0,005 km/s = 0,005.1000 = 5 m/s$

$⇒$ $18km/h= 5 m/s$

* $9km/h= 2,5 m/s$

(Vì $18$ gấp $9$ $2$ lần, $⇒$ $9km/h = 5 : 2 m/s = 2,5 m/s$)

* $8m/s= 28,8 km/h$ (Ở câu $3$)

* $4m/s= 14,4m/h$

(Vì $8$ gấp $4$ $2$ lần, $⇒$ $4m/s = 28,8 : 2 km/h = 14,4 km/h$)

* $6 m/s =km/h$

$6 m/s = 6 : 1000 km/s = 0,006 km/s$

$0,006 km/s = 0,006.3600= 21,6 km/h$

$⇒ 6 m/s =21,6 km/h$

* $15m/s=54 m/h$ (Ở câu $2$)

* $14 m/s = km/h$

$14 m/s = 14 : 1000 km/s = 0,014 km/s$

$0,014 km/s = 0,014 . 3600 m/s = 50,4 km/h$

$⇒$ $14 m/s = 50,4 km/h$