Simplify the following text for a Grade 4 native English-speaking person.
Original: = 3.6 kmÂ hâ ' 1 ( exactly ) â 3.2808 feet per second ( approximately ) â 2.2369 miles per hour ( approximately ) â 1.9438 knots ( approximately )
Simplified: â â 3.2808 â feet per second ( approximately ) â â 2.2369 â miles per hour ( approximately ) = â 3.6 â kmÂ hâ ' 1 ( exactly )