marnie can walk 1km/m faster the jon. She completes a 20km hike 1 hour before him. Write an equation and solve it to find there walking speeds.

i cannot seem to solve this ahh (Headbang) plz help me (Speechless)

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- Jun 19th 2010, 10:11 PMLaylaSamQuadratic help!!
marnie can walk 1km/m faster the jon. She completes a 20km hike 1 hour before him. Write an equation and solve it to find there walking speeds.

i cannot seem to solve this ahh (Headbang) plz help me (Speechless) - Jun 19th 2010, 10:50 PMGrandad
Hello LaylaSamSuppose that Jon walks at $\displaystyle x$ kph. Then Marnie walks at $\displaystyle x+1$ kph.

Using the formula

$\displaystyle \text{time} = \dfrac{\text{distance}}{\text{speed}}$Marnie takes $\displaystyle \frac{20}{x+1}$ hours, and Jon takes $\displaystyle \frac{20}{x}$ hours.

Since Jon takes $\displaystyle 1$ hour more than Marnie, we get:

$\displaystyle \dfrac{20}{x}=\dfrac{20}{x+1}+1$Now multiply both sides by $\displaystyle x(x+1)$ to get rid of fractions:

$\displaystyle 20(x+1)=20x+x(x+1)$

$\displaystyle \Rightarrow 20x+20=20x+x^2+x$

$\displaystyle \Rightarrow x^2+x-20=0$

$\displaystyle \Rightarrow (x+5)(x-4)=0$

$\displaystyle \Rightarrow x = 4$, since $\displaystyle x=-5$ is impossible.

So Jon walks at 4 kph and Marnie at 5 kph.

Grandad - Jun 19th 2010, 10:52 PMLaylaSam
Omg ur a genious!!! :)