SOLUTION: Hi, My daughter who is in sixth grade got this question: A lorry travels from Town A to Town B in 4 & 1/5 hrs. A car travels from Town B to Town A in 3 hrs. If both started at th

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Question 501780: Hi,
My daughter who is in sixth grade got this question:
A lorry travels from Town A to Town B in 4 & 1/5 hrs. A car travels from Town B to Town A in 3 hrs. If both started at the same time, after how long did they pass across each other? She is not allowed to use formulas and equations involving x, y etc. Can you please explain how to solve this without using equations?
Thanks.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A lorry travels from Town A to Town B in 4 & 1/5 hrs.
A car travels from Town B to Town A in 3 hrs.
If both started at the same time, after how long did they pass across each other?
:
I can't see how you can solve this without some equations, and why would you not want to? I assume we can use numbers and rules that govern there relationships.
Anyway, there is mathematical relationship between these values which is used in electronics, called the "product over sum" relationship
:
%284.2%2A3%29%2F%284.2%2B3%29 = 12.6%2F7.2 = 1.75 hrs travel time when they met
:
:
:
I admit I used algebra equations to confirm that this is right, in case you're interested.
Choose a value for the distance between the towns, I chose 21 mi a multiple of 4.2 and 3
Found the speed: 21/4.2 = 5 mph and 21/3 = 7 mph, let t = time for them to meet
5t + 7t = 21
12t = 21
t = 21%2F12
t = 1.75 hrs