In a race of three horses, the first beat the second by metres and the third by metres. If the second beat the third by metres, what was the length, in metres, of the racecourse?
In a race of three horses, the first beat the second by metres and the third by metres. If the second beat the third by metres, what was the length, in metres, of the racecourse?
Entered answer:
Solution
We have three horses in a race with the following results:
First horse beats the second horse by 11 metres
First horse beats the third horse by 90 metres
Second horse beats the third horse by 80 metres
We need to find the length of the racecourse.
Let's think about what happens when the first horse finishes the race:
When the first horse crosses the finish line:
The second horse is 11 metres behind the finish line
The third horse is 90 metres behind the finish line
This means the second horse is actually 79 metres ahead of the third horse at this moment.
Since the first horse beat the second by m and the third by m, the difference between second and third positions is: metres.
Here's where it gets interesting:
We know the second horse beats the third by 80 metres when the second horse finishes
But the second horse is already 79 metres ahead of the third horse
So the second horse needs to gain only 1 more metre on the third horse
Key Question: In what distance does the second horse gain 1 metre on the third horse?
From our earlier observation, when the first horse runs the final 11 metres to finish:
The second horse covers some distance less than 11 metres
The third horse covers even less distance
The second horse gains 1 metre on the third horse in this span
Since the first horse gains 11 metres on the second horse over the entire race, and in this same race the second horse gains 1 metre on the third horse, we can set up a proportion:
If the second horse gains 1 metre on the third horse when the first horse gains 11 metres on the second horse, then:
For the second horse to gain 80 metres on the third horse, the distance would be:
metres
Therefore, the length of the racecourse is 880 metres.