SOLUTION: At the airport, Person A and Person B are walking at the same speed to catch their flight, but Person B decides to step onto the moving sidewalk, while Person A continues
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Question 1138861: At the airport, Person A and Person B are walking at the same speed to catch their flight, but Person B decides to step onto the moving sidewalk, while Person A continues to walk on the stationary sidewalk. If the sidewalk moves at 1 meter per second, and it takes Person B 30 seconds less to walk the 360-meter distance, at what speed are Person A and Person B walking? Answer by ikleyn(52794) (Show Source):
Let x be the speed of A and B (the same (!) ) walking on the stationary sidewalk (in meters per second).
Then the effective speed of B on the moving sidewalk is (x+1) m/s.
The time equation is
- = 30 seconds.
Cancel the factor of 30 in both sides and then multiply both sides by x*(x+1).
12(x+1) - 12x = x*(x+1)
12 = x^2 + x
x^2 + x - 12 = 0
(x+4)*(x-3) = 0.
The roots are x= -4 and x= 3, but only positive value x= 3 is the meaningful solution.
ANSWER. The speed of A and B walking on stationary sidewalk is 3 meters per second.
CHECK. - = 120 - 90 = 30 seconds. ! Correct !
Solved.
(Actually, it is very high speed for walking person.
Usual speed walking is about 1 m/s, as everybody knows.
I suspect that it would be much more realistic to have feet in this problem instead of meters !)
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Using "time" equation is the STANDARD method of solving such problems.
