Question

At $9am$ a car (A) began a journey from a point, traveling at $40$mph. At $10am$ another car (B) started traveling from the same point at $60$mph in the same direction as car (A). At what time will car B pass car A?

Answer 1

From the given information we know that the distance D1 travelled by car A will be,
$D1=40t$
Given that car B starts at 10am and will therefore have spent one hour less then car A when it passes it, here the distance D2 travelled by car B is given by,
$D2=60(t-1)$
When car B passes car A, they are at the same distance from the starting point and therefore D1 = D2 here by substituting the values of D1 and D2 we get the equation as,
$40t=60(t-1)$
$40t=60t-60$
$20t=60$
$t=3$
As the time when car A started the journey is 9am we add the time $t=3$ hours to it and get the time as 12am.
Answer Car B will pass the car A at $12am.$