Video Explanation

Text Explanation

This is a fun stoichiometry-like problem! =) 

Our goal is to convert 100 ft in 2 seconds to the approximate speed in miles per hour. This is a huge hint that we can use rough estimates later in this problem. 

Let’s begin by converting feet per second to feet per hour. Let x = feet the object travels in 1 hr. 

Since 1 hr = 60 min × 60 seconds = 3600 seconds, we can substitute that for 1 hour. 

We have a proportion, so by the rules of Horizontal Cancellation, we can divide both denominators by 2 to get: 

So, x = 100 × 1800 = 180,000 ft/hr. 

But, we want the answer in miles/hr, so we're going to have to convert from feet to miles.  Well, the prompt tells us 1 mile = 5280 ft. That's a tough number to divide by, but have no fear, we can estimate!  

Using round numbers, we can easily determine that 180,000 ft/hr ×  = 36 miles/hr. It follows that will be slightly less than 36. The closest answer choice is 34, and that’s our answer!