Algebra Demystified 2nd Ed

Chapter 11 QuaDraTiC appliCaTionS 443

1

7

0 1

7

77 343 210

0114930

0511

2

2

() ()

()(

=−−

=−−

=−

rr

rr

rr++

−= +=

6

50 60

)

rr 11 (Thisdoesnotleadtooasolution.)

r= 5

The jogger’s average speed to the park was 5 + 1 = 6 mph.

PRACTICE

1. A man rode his bike 6 miles to work. The wind reduced his average speed
   on the way home by 2 mph. The round trip took 1 hour 21 minutes. How
   fast was he riding on the way to work?


2. On a road trip a saleswoman traveled 120 miles to visit a customer. She
   averaged 15 mph faster to the customer than on the return trip. She
   spent a total of 4 hours 40 minutes driving. What was her average speed
   on the return trip?


3. A couple walked on the beach from their house to a public beach four
   miles away. They walked 0.2 mph faster on the way home than on the
   way to the public beach. They walked for a total of 2 hours 35 minutes.
   How fast did they walk home?


4. A family drove from Detroit to Buffalo, a distance of 215 miles, for the
   weekend. They averaged 10 mph faster on the return trip. They spent a
   total of seven hours on the road. What was their average speed on the
   trip from Detroit to Buffalo? (Give your solution accurate to one decimal
   place.)


5. Boston and New York are 190 miles apart. A professor drove from his
   home in Boston to a conference in New York. On the return trip, he faced
   heavy traffic and averaged 17 mph slower than on his way to New York.
   He spent a total of 8 hours 5 minutes on the road. How long did his trip
   from Boston to New York last?

✔SOLUTIONS

1. Let r represent the man’s average speed on the way to work. Then r − 2
   represents the man’s average speed on his way home. The distance each
   way is 6 miles, so the time he rode to work is^6
   r

, and the time he rode

PRACTICE

1. A man rode his bike 6 miles to work. The wind reduced his average speed
   on the way home by 2 mph. The round trip took 1 hour 21 minutes. How

PRACTICE

1. A man rode his bike 6 miles to work. The wind reduced his average speed