Speed of car

The car went to a city that was 240 km away. If his speed increased by 8 km/h, it would reach the finish one hour earlier. Determine its original speed.

Correct answer:

v =  40 km/h

Step-by-step explanation:

s = vt  240 = vt 240 = (v+8)(t−1)  240 = (v+8)(240/v−1)  240⋅ v=(v+8)⋅ (240−v)  240⋅ v=(v+8)⋅ (240−v) v2+8v−1920=0  a=1;b=8;c=−1920 D=b2−4ac=82−4⋅1⋅(−1920)=7744 D>0  v1,2​=2a−b±D​​=2−8±7744​​ v1,2​=2−8±88​ v1,2​=−4±44 v1​=40 v2​=−48  v>0  v=v1​=40=40 km/h

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