Question 337035
since the cars are travelling in same direction Car 1 gains 10 km every hour.
in 1/4 hour it will gain 10/(1/4)= 2.5 km.
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Let car 1 travel x km at speed of 65 km/h
car2  will travel x-2.5 km in the same time
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time = distance /speed
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x/65 = (x-2.5)/55
55x=65(x-2.5)
55x=65x-162.5
add -65x
55x-65x=65x-65x-162.5
-10x=-162.5
divide by -10
x= -162.5/-10
x=16.25 km. the distance car 1 has to travel to be 15 minutes ahead.