Tanisha2819 wrote:
Hello
Bunuel Thank you so much with the solution. I solved it using rather long method of finding out in how much time they meet and then subtracting 1.5 hrs from that to get the distance b/w them. Got the wrong answer because of calculation mistake. I do understand the concept of relative speed applied here that we are adding up their speeds because they are moving towards each other.
But why we multiplied their relative speed with 1.5 hrs, I am a little lost here because i thought that we multiply that time with the relative speed in which we want to find out the distance covered by both the people and here we are not doing that, we want to find out how far apart F & A would be from each other 1.5 hrs before they meet. I am not able to grasp the logic behind this. I would be really thankful if you could help me understand this as this method is clearly a time saver and a quicker way to get to the right answer.
Thanks
BunuelI'll try again.
The reason we multiply the relative speed by 1.5 hours is to calculate the distance Fanny and Alexander cover together in that time period before they meet. Since they are moving towards each other, their relative speed is the sum of their individual speeds. By multiplying this combined speed (90 mph) by the time remaining before they meet (1.5 hours), we find out how much distance remains between them at that point. This method gives us the distance between Fanny and Alexander 1.5 hours before they meet.
In other words, 1.5 hours before they meet, the distance between Fanny and Alexander is the distance they would cover together in 1.5 hours. Since they cover that distance at 90 miles per hour, then distance = time × speed = 1.5 × 90 = 135 miles.
Hope it helps.