SOLUTION: Lori was walking down the street on her way to the grocery store. As she got to a crosswalk, she noticed a van coming from her left, passing under a railroad overpass just as she s

Algebra ->  Numeric Fractions Calculators, Lesson and Practice -> SOLUTION: Lori was walking down the street on her way to the grocery store. As she got to a crosswalk, she noticed a van coming from her left, passing under a railroad overpass just as she s      Log On


   



Question 1020546: Lori was walking down the street on her way to the grocery store. As she got to a crosswalk, she noticed a van coming from her left, passing under a railroad overpass just as she started to cross the street. As she finished crossing the street, the van reached the crosswalk behind her. She turned left when she reached the sidewalk. It took her 15 seconds to cross the street and 2 minutes 20 seconds to reach the overpass. She walks 3 miles per hour. How fast was the van going? (Assume it was traveling at a constant speed.)
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Lori was walking down the street on her way to the grocery store.
As she got to a crosswalk, she noticed a van coming from her left, passing under a railroad overpass just as she started to cross the street.
As she finished crossing the street, the van reached the crosswalk behind her.
She turned left when she reached the sidewalk.
It took her 15 seconds to cross the street and 2 minutes 20 seconds to reach the overpass.
She walks 3 miles per hour.
How fast was the van going? (Assume it was traveling at a constant speed.)
:
After reading this we can summarize this
The Van took 15 sec to travel from the overpass to the crosswalk,
The walker took 140 sec (2'20") to travel from the crosswalk to the overpass
let v = speed of the van
:
An inverse ratio equation. time is inversely proportional to speed
v%2F3 = 140%2F15
Cross multiply
15v = 3 * 140
v = 420/15
v = 28 mph is the speed of the van