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]
