Grace roller skates 55.5km with a constant speed of 15.5 km/h and another 26.4 km with a constant speed of 8 km/h. how much time in total does she take to travel these distances?

This is a three step problem. Luckily, the mathematics are pretty basic since we need not worry about acceleration in this problem, as the speed at which Grace roller skates is constant.

We start with part one, the first data given.

Grace travels 55.5km going 15.5 km/hr. In order to find out how much time it takes for Grace to travel this far, we can use a kinematics equation.

Substitute some numbers in:


So from here, we would multiply both sides by "t":


And then divide both sides by 15.5:


Remember that this is in hours, as the original velocity given was in km/hr.

Then, we do the same for the second set of data, coming to:


Again, this is in hours.

Finally, to find the answer to how long it took Grace to do this, we simply add the above solutions together and discover that it took her 6.88 hours (multiply by 60 minutes to find out she roller skated for 412.8 minutes) to travel that far. Wow! Grace has some admirable endurance!

It was ernest rutherford