Answer:
d= 12.50 miles
Step-by-step explanation:
Kinematic equation of uniform motion (constant speed) :
v= d/t Formula (1)
v: velocity in miles per hour (mph)
d: distance in miles
t: time in hours
Data
v= 50 mph
t= 0.25 hours
Problem development
We replace data in formula (1)
50 mph=d/0.25 hour
d= 12.5 miles
d= 12.50 miles
The mistake is in Step 1. The solver should have also squared when squaring the other side of the equation.
For this case we have:
If after 2 hours the marathon runner has traveled 22 kilometers we have:
2h -----------> 22km
Applying a rule of three, we can know the time it takes to run 42km. So, we have:
2h -----------> 22km
x -------------> 42km
Where "x" is the time it takes to travel 42km. Resolving we have:
Thus, after 3.82 hours the marathon runner will travel 42km.
Answer:
3.82 hours