Bunuel
Route 1: City Centre – Market Square – Songbird Park – City Centre (3 miles)
Route 2: City Centre – Laurel Lane – Market Square – City Centre (3 miles)
Route 3: City Centre – City Hall – Laurel Lane – City Centre (3 miles)
Route 4: City Centre – City Hall – Market Square – Laurel Lane – City Centre (4 miles)
Route 5: City Centre – Songbird Park – Market Square – Laurel Lane – City Centre (4 miles)
A cross-country runner trains by running three predetermined routes every day. Each day, her total distance travelled is 10 miles. She does not run any of the routes more than two days in a row and never avoids a route two days in a row.
For the
City Centre, select the number of times the runner will run towards the city centre over the span of any 3-day period. For
Laurel Lane, select the number of times the runner will run towards Laurel Lane over the span of any 3-day period. Make only two selections, one in each column.
Each day, the runner's total distance travelled is 10 miles and runs 3 predetermined routes every day. This means, out of the 3 runs, 2 runs are of 3 miles i.e., from Route 1, 2, or 3 (2 routes out of 3 routes will be selected daily). And one run will be of 4 miles i.e., route 4 or route 5.
2 * (3 miles) + (4 miles) = 10 miles
Now, she does not run any of the routes more than two days in a row and never avoids a route two days in a row. So, in selecting 2 out of 3 routes from Route 1, 2, and 3, we should keep in mind the limitation. This can only be done in a rotatory pattern of 3 days
similar to that of below:
Day 1: Route 1 and 2
Day 2: Route 2 and 3
Day 3: Route 1 and 3
Basically in all 3 days pattern similar to this, every route out of Route 1, 2, and 3, will be run by the runner exactly two times.
Now, talking about the 4 miles route i.e., Route 4 and 5. Out of the two, exactly one will be selected daily. By keeping in mind the rule "she does not run any of the routes more than two days in a row and never avoids a route two days in a row", this can be done in two ways as below:
1. Alternately choosing between Route 4 and Route 5 each day.
2. Consecutive 2 days on Route 4 and then consecutive 2 days on Route 5 (and vice versa)
Now, answering the questions: the number of times the runner will run towards the city centre over the span of any 3-day period:
As routes have city center, so running every route the runner will approach toward the city centre. So, 3 (routes) * 3 (days) = 9 times
The number of times the runner will run towards Laurel Lane over the span of any 3-day period: Only Route 2 and 3 have the (out of the 3 mile route) have the Laurel Lane. And Each route is run twice over the 3 days period. So, 4 times through 3 miles route in 3 days period.
and on the 4 mile route (i.e., route 4 or 5) daily run, every day the runner will run towards Laurel Lane over the span of any 3-day period
So, Total = 4 + 3 = 7