Solve High School Lockers Calculus Problem

  • Thread starter Thread starter whisperblade
  • Start date Start date
  • Tags Tags
    Calculus
AI Thread Summary
The problem involves 1000 lockers and students toggling the doors based on divisibility by their locker numbers. Each locker starts closed, and students change the state of lockers that divide their own number. A suggested approach is to simulate the first 15-20 students to identify a pattern in the toggling process. The solution hinges on understanding how many times each locker is toggled, which relates to the number of divisors it has. Ultimately, only lockers that are perfect squares will remain open at the end.
whisperblade
Messages
11
Reaction score
0
Hi everyone, i recently got this problem from my college professor and I am either incredibly rusty or just don't know how to do this. I've tried to set up some sort of equation using f(x) but i just can't make anything fit or account for everything. any help would be appreciated.

the question follows:
A high school has 1000 students and each has a numbered locker where they keep various smelly items. Fortunately all the locker doors are shut. One by one, each student walks past the lockers, and either opens or shuts (depending on its previous position) the door of any locker that divides their own locker number. How many lockers are open at the end?
 
Physics news on Phys.org
My daughter got this same problem a few weeks back. Suggest you just plug-n-chug to map out the 1st 15-20 students until you see the pattern. At least, that's how we did it.
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...

Similar threads

Replies
16
Views
13K
Replies
1
Views
3K
Replies
7
Views
17K
Replies
3
Views
2K
Replies
3
Views
2K
Back
Top