Multiple units used for the same quantity in a question is an irritant to most of us. Today, I will discuss how to quickly convert from one to another so that we can focus on the actual question rather than getting lost in the units!

I will show how to do it using a couple of examples.

Example 1:

Jodie runs her Prius 90 miles in two hours. In how many seconds, does she cover 132 feet? (Given 1 mile = 5280 feet)

In this question, I know her speed is 90 miles/2 hours. I need it in feet/second because distance is given in feet (which is 132 feet) and the answer is asked in seconds.

In place of 1 mile, we simply write 5280 feet and in place of 1 hour, we write 3600 seconds. (We know 1 hour has 60 minutes and 1 minute has 60 seconds, therefore, 1 hour has 60 x 60 = 3600 seconds). Voila! The whole thing has got converted to feet/sec.

We get that Jodie's speed is 66 feet/sec. Now, to solve the question we can simply use the Time-Speed-Distance formula which is, Time = Distance/Speed = 132 feet/66 feet per sec = 2 secs.

Example 2: Julia drives at a speed of 132 feet/sec. How many miles away is she from her home, if it will take her 2 hours to reach home? (Given 1 mile = 5280 feet)

Here we have Julia's speed in feet/sec and we need to convert it to miles/hour.

If 1 mile = 5280 feet, then 1 foot = 1/5280 miles and if 1 hour = 3600 seconds, then 1 second = 1/3600 hours

Now, using the Time-Speed-Distance formula again, Distance = Speed x Time = 90 miles/hour x 2 hours = 180 miles

Note: The units are also a part of the equation. We just don't notice them. For example, given below is what happens when we use the formula above,

I will show how to do it using a couple of examples.

Example 1:

Jodie runs her Prius 90 miles in two hours. In how many seconds, does she cover 132 feet? (Given 1 mile = 5280 feet)

In this question, I know her speed is 90 miles/2 hours. I need it in feet/second because distance is given in feet (which is 132 feet) and the answer is asked in seconds.

In place of 1 mile, we simply write 5280 feet and in place of 1 hour, we write 3600 seconds. (We know 1 hour has 60 minutes and 1 minute has 60 seconds, therefore, 1 hour has 60 x 60 = 3600 seconds). Voila! The whole thing has got converted to feet/sec.

We get that Jodie's speed is 66 feet/sec. Now, to solve the question we can simply use the Time-Speed-Distance formula which is, Time = Distance/Speed = 132 feet/66 feet per sec = 2 secs.

Example 2: Julia drives at a speed of 132 feet/sec. How many miles away is she from her home, if it will take her 2 hours to reach home? (Given 1 mile = 5280 feet)

Here we have Julia's speed in feet/sec and we need to convert it to miles/hour.

If 1 mile = 5280 feet, then 1 foot = 1/5280 miles and if 1 hour = 3600 seconds, then 1 second = 1/3600 hours

Now, using the Time-Speed-Distance formula again, Distance = Speed x Time = 90 miles/hour x 2 hours = 180 miles

Note: The units are also a part of the equation. We just don't notice them. For example, given below is what happens when we use the formula above,

nice! I've been wondering how to do this easily

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