Bunuel wrote:
Tanisha2819 wrote:
Bunuel wrote:
Official Solution:Fanny and Alexander are 360 miles apart and are both traveling towards each other in a straight line. Fanny is traveling at a constant rate of 25 miles per hour, while Alexander is traveling at a constant rate of 65 miles per hour. How far apart will they be exactly 1.5 hours before they meet? A. 135 miles
B. 90 miles
C. 70 miles
D. 65 miles
E. 25 miles
Let's keep it simple! The question asks how far apart Fanny and Alexander will be exactly 1.5 hours before they meet. Since their combined speed is 25 + 65 = 90 miles per hour, 1.5 hours prior to their meeting, they will be 90*1.5 = 135 miles apart.
Hi
Bunuel Answer: A
Hi
Bunuel Thank you for the solution.Could you please help me understand the concept applied in this solution? Why did we add up the speeds and then multiplied the result with 1.5 hrs, which are the hrs. spent before they meet.
Thank you
BunuelWhen two objects move towards each other, you can add their speeds together to find out how quickly they're closing the gap between them. Fanny and Alexander together reduce the distance between them by 90 miles every hour (25 mph for Fanny + 65 mph for Alexander).
So, if you look 1.5 hours before they meet, they'd be 135 miles apart because in that time they would cover that distance at their combined speed. This is why we add their speeds and then multiply by 1.5 hours.
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
Bunuel