SOLUTION: A car takes 2 hours less for a journey of 300km, if its speed is increased by 5 km/h from its usual speed. Find its usual speed.
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Question 230078: A car takes 2 hours less for a journey of 300km, if its speed is increased by 5 km/h from its usual speed. Find its usual speed.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = it's usual speed
Let = it's usual time for 300 km journey
given:
(1) km
(2)
-------------------------
This is 2 equations and 2 unknowns, so it's solvable
Expand (2)
(2)
(2)
substitute (1) in (2)
Plug this back into (1)
(1)
Solve using quadratic formula
(the negative answer can't be used)
It's usual speed is 25 km/hr
check answer:
(1) km
hrs
(2)
OK
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