Answer:
Joan drive with a speed of 55 miles per hour.
Step-by-step explanation:
Given:- Travelling time (t) = 4 hours.
Travelled distance (d) = 480 miles.
Speed of Justin is 10 miles per hour faster than Joan.
To find:- Speed of Joan = ?
Solution:-
Let speed of Joan be x,
therefore speed of Justin = x+10 ---------------(from given)
Now, Total speed of Joan and Justin = x+x+10
Total speed of Joan and Justin = 2x+10 ------------(1)
Now formula for speed is,
Speed = [tex]\frac{distance}{time}[/tex]
[tex]2x+10=\frac{480}{4}[/tex] -------------(from 1 and given)
[tex]2x+10=120[/tex]
[tex]2x=120-10[/tex]
[tex]2x=110[/tex]
[tex]\therefore x=\frac{110}{2}[/tex]
[tex]\therefore x= 55[/tex]
as x is the speed of Joan,
Therefore Joan drive with a speed of 55 miles per hour.
