A car is traveling at 45 miles/hr. How fast is it moving measured in [tex][tex]$km / hr$[/tex][/tex]? (Use 1 mile [tex]=1.6 \, km[/tex])

A. [tex]72 \, km / hr[/tex]
B. [tex]20.12 \, m / s[/tex]
C. [tex]72 \, km / hr[/tex]
D. [tex]28.125 \, km / hr[/tex]
E. [tex]72.42 \, km / hr[/tex]



Answer :

To convert the speed of a car from miles per hour to kilometers per hour, we can use the conversion factor that 1 mile is equal to 1.6 kilometers. Here are the steps to find the speed in kilometers per hour:

1. Determine the car's speed in miles per hour:
[tex]\[ \text{Speed in miles per hour} = 45 \, \text{miles/hr} \][/tex]

2. Use the conversion factor to convert miles per hour to kilometers per hour. The conversion factor is 1 mile = 1.6 kilometers.

3. Multiply the car's speed by the conversion factor:
[tex]\[ \text{Speed in kilometers per hour} = 45 \, \text{miles/hr} \times 1.6 \, \text{km/mile} \][/tex]
[tex]\[ \text{Speed in kilometers per hour} = 45 \times 1.6 \, \text{km/hr} \][/tex]
[tex]\[ \text{Speed in kilometers per hour} = 72 \, \text{km/hr} \][/tex]

So, the speed of the car in kilometers per hour is:
[tex]\[ \boxed{72 \, \text{km/hr}} \][/tex]

Among the given options:
- [tex]$20 \, \text{km/hr}$[/tex]
- [tex]$20.12 \, \text{m/s}$[/tex]
- [tex]$72 \, \text{km/hr}$[/tex]
- [tex]$28.125 \, \text{km/hr}$[/tex]
- [tex]$72.42 \, \text{km/hr}$[/tex]

The correct answer is:
[tex]\[ 72 \, \text{km/hr} \][/tex]