a bicyclist can make her bike move at 30 miles per hour. how many feet per second is this?

Question

Change miles to feet abe hours to minutes to seconds

Answer 1

This is the way I learned to convert numbers into different units, if you don't understand a step please ask me and I will gladly explain it.

 

1. Is to determine what your starting point is, and where you want to end up. So 30 miles/hour ---->  ____ feet/second

 

2. Is to set the problem up so that you can cancel out the in between units it takes to get to the end point. (the hour to min to sec).  Since this is a two part problem (changing miles to feet & hours to seconds) I will show you the miles part first.  Some basic things you have to know are: 5,280 feet in 1 mile, 60 minutes in an hour, and 60 seconds in 1 minute.

 

30 miles       5,280 feet         158,400 feet

----------  X  -------------  =   ----------------

1 hour          1 mile                1 hour

 

Do you see how the miles cancel out? I put them in italics to show you that since they match, they can be crossed out, and that will leave you with 30 x 5,280 feet = 158,400 feet on top, & 1 hour x 1 = 1 hour on bottom.

 

The second part is the same as the first but we will change the hour to seconds. Since there are minutes between an hour and seconds, there will be 1 extra step this time.

 

158,400 feet        1 hour       1 minute         158,400 feet           2,640 feet          44 feet

--------------   x    -------    x  ----------    =  ---------------     =   ------------    =   -----------

1 hour             60 minutes    60 seconds     60 minutes              60 seconds        1 second

 

The hours cancel out, as well as the minutes, and that leaves us with seconds on bottom.  The number of minutes and seconds need to be divided from the number of feet to figure out how many feet could be traveled in 1 second.

 

158,400 feet/ 60 minutes = 2,640 feet/ 1 minute

 

2,640 feet/ 60 seconds  =  44 feet/ 1 second

 

 

Hope that helps!! It takes longer to explain than to actually do it.

 

Answer 2

30 miles * 5280 feet * 1 hour  * 1 min

  hour          mile         60 min    60 sec

 

cancel units for feet/sec

 

44 ft/sec

Answer 3

30 mile/hour * 5280 ft/mile * 1 hour/60 minute * 1 minute/60 sec = 44 ft/sec

 

Note how the units divide out, leaving ft on the top and sec on the bottom; you always check this.

 

Also:  a shortcut for this problem is to know that 60 mph = 88 ft/sec;  30 mph is half of 60 mph, so you take half of 88 ft/sec = 44 ft/sec.