Question

Eli and dex are travelling from point a to b, which are 360 kms apart. travelling at a certain speed eli takes 30 mins less than dex to reach point

b. if eli doubles her speed, she will take 2 hours 30 mins less than dex to reach point

b. at what speed was eli driving from point a to b ?

Answer 1

Let the speed of Eli be x and the speed of dex be y then :

Time taken by Eli = 360/x

Time taken by Dex is = 360/y

Eli takes 0.5 hrs less than Dex therefore :

360/x = 360/y - 0.5...... 1

If Eli doubles his speed :

Time = 360/2x = 180/x

This is 2.5 less than Dex hence :

180/x = 360/y - 2.5

Lets get the value of y from this :

180y = 360x - 2.5xy

180y + 2.5xy = 360x

Y(180 + 2.5x) = 360x

Y = 360x / (180 + 2.5x)

Substituting this in 1 :

360/x = 360(180 + 2.5x) /360x - 0.5

360 = 180 + 2.5x - 0.5x

360 - 180 = 2x

180 = 2x

x = 180/2

X = 90km/h

Eli drives at 90km/h

Answer 2

90km/hr

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