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Masha biked 20 km 20 minutes faster than Dasha biked 20 km. Find the speed of each cyclist if one biked 2 km/h faster than the other.

 Jul 28, 2020
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20 km / (r+2)   + 1/3  =   20km/ (r)                     (1/3 hr = 20 minutes)

 

20 (r)  + 1/3( r)(r+2) = 20 r +40

20 r   + 1/3 r^2 + 2/3 r  = 20 r + 40

1/3 r^2 + 2/3 r -40 = 0                              quadratic formula shows r = 10      r+2 = 12

 Jul 28, 2020

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