In the morning, Maria drove to a business appointment at 30 mph. Her average speed on the return trip in the afternoon was 20 mph. The return trip took [tex]\frac{1}{2}[/tex] hour longer because of heavy traffic. How far did she travel to the appointment?



Answer :

Let's denote the distance to Maria's appointment as [tex]\( d \)[/tex] miles.

1. Time taken to travel to the appointment in the morning:

Maria drives at a speed of 30 mph. Therefore, the time taken to travel to the appointment in the morning can be calculated using the formula:
[tex]\[ t_{\text{morning}} = \frac{d}{\text{speed}_{\text{morning}}} = \frac{d}{30} \, \text{hours} \][/tex]

2. Time taken to return from the appointment in the afternoon:

On the return trip, Maria's speed was 20 mph. Thus, the time taken for the return trip is:
[tex]\[ t_{\text{afternoon}} = \frac{d}{\text{speed}_{\text{afternoon}}} = \frac{d}{20} \, \text{hours} \][/tex]

3. Relationship between the morning and afternoon travel times:

It is given that the return trip in the afternoon took [tex]\( \frac{1}{2} \)[/tex] hour longer than the morning trip. So, we have:
[tex]\[ t_{\text{afternoon}} = t_{\text{morning}} + 0.5 \][/tex]

4. Substituting the expressions for [tex]\( t_{\text{morning}} \)[/tex] and [tex]\( t_{\text{afternoon}} \)[/tex] into the equation:

Substituting the expressions [tex]\( t_{\text{morning}} = \frac{d}{30} \)[/tex] and [tex]\( t_{\text{afternoon}} = \frac{d}{20} \)[/tex] into the equation from step 3, we get:
[tex]\[ \frac{d}{20} = \frac{d}{30} + 0.5 \][/tex]

5. Solving the equation for [tex]\( d \)[/tex]:

To eliminate the fractions, we can multiply every term by 60 (the least common multiple of 20 and 30):
[tex]\[ 60 \left( \frac{d}{20} \right) = 60 \left( \frac{d}{30} \right) + 60 \left( 0.5 \right) \][/tex]

Simplifying each term:
[tex]\[ 3d = 2d + 30 \][/tex]

Subtract [tex]\(2d\)[/tex] from both sides to isolate [tex]\(d\)[/tex]:
[tex]\[ d = 30 \][/tex]

Therefore, the distance to Maria's business appointment is [tex]\( 30 \)[/tex] miles.