A car made a run of 390km in x hours. If the speed had been 4 km/hour more it would have taken 2 hours less for the journey . Find x

 

 

Asked by appujinju4 | 13th Jan, 2019, 04:10: PM

Expert Answer:


Let speed of car be y

Therefore 390/x=y

and

390/x-2=y+4

subtract both equations to get

390 over straight x minus fraction numerator 390 over denominator straight x minus 2 end fraction equals negative 4
390 open parentheses fraction numerator negative 2 over denominator straight x squared minus 2 straight x end fraction close parentheses equals negative 4
straight x squared minus 2 straight x minus 195 equals 0

(x-15)(x+13)=0

Therefore x is 15 hours as x cannot be negative as it is time.

Answered by Arun | 13th Jan, 2019, 06:44: PM