1. A car travels 20 kph faster than a truck. The car covers 480 km in two hours lessthan the time it takes the truck to travel the same distance. How fast does the car travel?

A. 44 kph B. 60 kph C. 80 kph D. 140 kph21. A 12 cm by 16

2. it takes mary 3 hours more to do a job than it takes jane. if they work together they can finish the same job in 2 hours. how long would it take mary to finish the job alone

a. 3 b. 5. c. 6 d.8

pls help me and show me computation

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Answers

2014-08-08T14:46:10+08:00
1. Let x be the time for the truck to cover the distance
x-2 is for the car's time to cover the distance

480/x-2 = 480/x + 20 Find the LCD and multiply it to each term (LCD=x²-2x)
480x = 480x-960+20x²-40x Transpose the equation on the right side to the left side and combine like terms
-20x²+40x+960=0  Multiply the equation by -1 so that the quadratic term is positive
20x²-40x-960=0  Divide the x² coeffiecient by the equation
x²-2x-48=0  Factor
(x+6)(x-8)  Solve
x= 8 or -6

Substitute the positive value in the equation
x=8

480km/6hr= 80 km/h (Car)
480km/8hr= 60 km/h (Truck)

So the answer is letter B.
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