Question

If you run $120\;$ feet in $4.8\;$ seconds, how many miles per hour would you be running?

Answer 1

Hint: There are $5280\;$ feet in a mile and $3600\;$ seconds in an hour which can be calculated by multiplying the total number of minutes in an hour with the total number of seconds in a minute $\left( 60\min \times 60\sec \right)$ . To solve this question, we need to convert feet to miles and seconds to an hour to get the required result.

Complete step by step answer:
We are given that the distance covered in 4.8 seconds is 120 feet and need to find the number of miles covered in the time period of one hour.
We will be using the concept of unitary method to solve the given question.
Let us calculate the distance covered in $1$ second. To calculate the same, we need to divide the distance given in the question with the time.
Applying the same, we get,
$\Rightarrow \dfrac{120feet}{4.8\sec }$
Multiplying the numerator and denominator of the above expression by 10, we get,
$\Rightarrow \dfrac{1200feet}{48\sec }=25$ feet per second.
Now, we need to calculate miles per second by dividing the feet per second to the number of feet in a mile.
Dividing the feet per second to the number of feet in a mile, we get,
$\Rightarrow \dfrac{25feetper\sec }{5280feet}=0.004734$miles per second.
Now, we need to convert the seconds in the above expression to hours.
 Multiplying the ratio above by $3600\sec$ , we get,
$\Rightarrow 0.00473\times 3600=17.045mph$

Therefore, I will be running $17.045\;$ miles per hour.

Note: We can also solve this problem with an alternative approach. Instead of directly converting feet into miles, one can also first convert feet into yards and the convert the measurement in yards to miles. The time can also be converted first to minutes and then to hours from seconds for simple calculations and better understanding.
We must also be very careful while converting values from one system of measurement to another as most students make the mistake of dividing or multiplying the fractions with the wrong conversion rates, which can lead to miscalculations and wrong answers.