A cross-country runner trains by running three predetermined routes every day.
Understand these conditions carefully.- Each day, her total distance travelled is 10 miles.
- She does not run any of the routes more than two days in a row (If on first day if she is running on route R1 she can continue on route R1 on next day)
- and never avoids a route two days in a row. (If she is not taking route R1 on first day then on next day she should take route R1 on next day
For the
City Centre (CC), select the number of times the runner will run towards the city centre over the span of any 3-day period. For
Laurel Lane (LL), 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.
Now if you observe the given routes. For every route that she takes, will eventually lead to city centre. Lets list down the counts in front of every route for both CC and LL
Route 1: City Centre – Market Square – Songbird Park – City Centre (3 miles) - Towards - (CC 1, LL-0)
Route 2: City Centre – Laurel Lane – Market Square – City Centre (3 miles) - Towards - (CC 1, LL-1)
Route 3: City Centre – City Hall – Laurel Lane – City Centre (3 miles) - Towards - (CC 1, LL-1)
Route 4: City Centre – City Hall – Market Square – Laurel Lane – City Centre (4 miles) - Towards - (CC 1, LL-1)
Route 5: City Centre – Songbird Park – Market Square – Laurel Lane – City Centre (4 miles) - Towards - (CC 1, LL-1)
Now,
Each day, her total distance travelled is 10 miles.This count of 10 is only possible with combination of 3 + 3 + 4 = 10
Therefore for each day she is taking 3 routes in any order.
lets form possible routes with given conditions 2 and 3. -
for 3 miles there are 3 options and for 4miles there are 2 options
number of possible routes = 3C2 * 2C1 = 6 routes.
Lets list down those routes.
1 - R1>R2>R4, 2-R2>R3>R4, 3-R1>R3>R4, 4-R1>R2>R5, 5-R2>R3>R5, 6-R1>R3>R5
well these 3 routes can arrange within themseleves but its not going to change anything that we need for answering the question.
Now lets take conditions for 3 days,
If she takes 1 - R1>R2>R4 on first day then on second day she could either take 5-R2>R3>R5 or 6-R1>R3>R5 and depending on selection of 2nd day we can make selection for 3rd day from options 3-R1>R3>R4 or 2-R2>R3>R4
but make sure you are not violating condition 2nd and 3rd.Day 1 -------------------------- Day 2 ------------------------------ Day 3
1 - R1>R2>R4 5-R2>R3>R5 3-R1>R3>R4
1 - R1>R2>R4 6-R1>R3>R5 2-R2>R3>R4
you can form other configurations like this if you want to.
lets now move on to calculation part for these two configurations that we have made for 3 days
1st - 1 - R1>R2>R4 ---------------- 5-R2>R3>R5 ---------------- 3-R1>R3>R4
Total CC, each route has 1 run toward cc so for this route there will be 9 running towards CC = 9
Total LL = 1 - R1>R2>R4 (0+1+1) 5-R2>R3>R5 (1+1+1) 3-R1>R3>R4 (0+1+1) = Total LL = 2+3+2 = 7
For confirming again lets check for 2nd configuration of 3 day route.
2nd - 1 - R1>R2>R4 ---------------- 6-R1>R3>R5 ---------------- 2-R2>R3>R4
Again Total CC, each route has 1 run toward cc so for this route there will be 9 running towards CC = 9
Total LL = 1 - R1>R2>R4 (0+1+1) 6-R1>R3>R5 (0+1+1) 2-R2>R3>R4 (1+1+1) = Total LL = 2+2+3 = 7
Therefore, For the City Centre, number of times the runner will run towards the city centre over the span of any 3-day period = 9.
and For Laurel Lane, number of times the runner will run towards Laurel Lane over the span of any 3-day period = 7