SOLUTION: Please help me solve this question: At 7:00 A.M., Brooke leaves home to go on a business trip driving 35 miles per hour. Fifteen minutes later, Bart discovers that Brooke forgot

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Question 189187This question is from textbook
: Please help me solve this question:
At 7:00 A.M., Brooke leaves home to go on a business trip driving 35 miles per hour. Fifteen minutes later, Bart discovers that Brooke forgot her presentation materials. He drives 50 miles per hour to catch up with her.If Bart is delayed 30 minutes with a flat tire, when will he catch up with Brooke.
This is the question exactly from the book.
This question is from textbook

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I can write two equations, one for Brooke:
(1) d%5Ba%5D+=+r%5Ba%5D%2At%5Ba%5D
and one for Bart,
(2) d%5Bb%5D+=+r%5Bb%5D%2At%5Bb%5D
The key to the problem is that Bart catches Brooke.
The distance that each drives is the same
The time Bart spends driving must equal the time
Brooke spends driving
given:
d%5Ba%5D+=+d%5Bb%5D mi
r%5Ba%5D+=+35 mi/hr
r%5Bb%5D+=+50 mi/hr
t%5Ba%5D+=+t%5Bb%5D+%2B+.75 hr
---------------------------
(1) d%5Ba%5D+=+r%5Ba%5D%2At%5Ba%5D
(1) d%5Ba%5D+=+35%2A%28t%5Bb%5D+%2B+.75%29
(1) d%28a%29+=+35t%5Bb%5D+%2B+26.25
and
(2) d%5Bb%5D+=+r%5Bb%5D%2At%5Bb%5D
(2) d%5Bb%5D+=+50t%5Bb%5D
And, since d%5Ba%5D+=+d%5Bb%5D
(2) d%5Ba%5D+=+50t%5Bb%5D
Subtract (1) from (2)
(2) d%5Ba%5D+=+50t%5Bb%5D
(1) d%28a%29+=+35t%5Bb%5D+%2B+26.25
(3) 0+=+15t%5Bb%5D+-+26.25
(3) 15t%5Bb%5D+=+26.25
(3) t%5Bb%5D+=+1.75
Bart's time driving is 1.75 hrs
If you add his delays,
1.75+%2B+.75+=+2.5
So, 2.5 hrs after Brooke left, Bart caught her
which was 7 AM + 2.5 = 9:30 AM
check answer:
Brooke's driving time was 2.5 hrs
(1) d%5Ba%5D+=+35%2A2.5
(1) d%28a%29+=+87.5 mi
and
(2) d%5Ba%5D+=+50t%5Bb%5D
(2) 87.5+=+50t%5Bb%5D
(2) t%5Bb%5D+=+1.75 hr
This is what I said Bart's driving time was, so
it checks