Question

Some physics kids were testing some changes they made to make their bikes go faster. Theyposted the following speeds on the class whiteboard. Who went the fastest? Scot went 15,000 m/hr George went 15 km/hr Fred went 4.3 m/s May went 13 km/hr

Answer 1

To do this, you need to make sure that all speeds are the same unit. Since there are three 2 speeds already in km/hr, it would be best that you match the other 2 speeds into that unit as well. 

Conversion of 15,000m/hr:
time is already in hours so you just need to make convert the meters to kilometers. 

$15,000\frac{m}{hr} * \frac{1km}{1,000m} = 15\frac{km}{hr}$

Conversion of 4.3m/s
$4.3 \frac{m}{s} * \frac{3,600s}{1hr} * \frac{1km}{1000m} = 15.48 \frac{km}{hr}$

Now that they are all the same value, you can see that Fred at 4.3m/s  was the fastest.