O-Level Additional Math

[CoffeeCat]

Ok lor I find Your questions interesting and challenging ( definitely not ok lor) so I am curious are you in some math enrichment program in sch or sth?

[OK Lor]

Hi CoffeCat,


Ya, currently in school Math Talent Program training. Find a wealth of resources here. 请多多指教. Thanks.

[Guan Hui]

Wa=D but i am not a talent but I am glad I am of help sometimes… still working on it=p

[CoffeeCat]

OK Lor:

Hi CoffeCat,


Ya, currently in school Math Talent Program training. Find a wealth of resources here. 请多多指教. Thanks.

whoa cool, but I have no idea which school has that program so which school are you from? Will be happy to assist you in your learning along with tutor guanhui. Will be cool if you can describe more about your program, broaden our horizon and more information for future prospective applicants to your schools =).

[OK Lor]

Hi CoffeeCat,


paiseh, from the questions asked, 不值一提 :oops:.

[ckh]

Hi, all,


This is an assignment question for my son in Sec 1. I would like to poll your understanding in interpreting this question, especially the last sentence:

Beginning of question:

Imagine a school with 1000 numbered, closed lockers, one for each of its students. Suppose all the students line up and go through the locker area to perform a specific task.

The first student will open all the locker doors.

The second student will close all the locker doors with even numbers.

The third student will change all the locker doors with numbers that are multiples of three. (Change means closing lockers that are open and opening locker doors that are closed.)

The fourth student will change the position of all the locker doors numbered with multiples of four, the fifth student will change the position of all the locker doors that are multiples of fives, and so on.

Every student goes through, reversing the lockers which correspond to his or her position in line until the 1000th student has passed through.

End of question.

To keep things short, I would like to identify the first 5 lockers' positions (whether opened or closed).

We would like to double check our understanding of the question

Thks and best rgds.

[corneyAmber]

2,3,5 Open

1 and 4 Closed

Correct?

[CoffeeCat]

ckh:

Every student goes through, reversing the lockers which correspond to his or her position in line until the 1000th student has passed through.

The last sentence indeed sound funny, but its valid for students whose numbers are very big.

I will say locker 1 and 4 are opened,
2, 3, 5 closed.

If you and your son has different interpretations it will be interesting to share with us.

[ckh]

Hi,


Thanks for your reply. This was what we got also.

[ckh]

Hi, dear CoffeeCat and ksi,


Indeed the last sentence sounds funny, and this is the reason we like to double check our interpretation. There are lots of solutions on the Internet that provided the same answers as yours, i.e. locker 1 and 4 are opened, 2, 3, 5 closed.

But because of the action on the last sentence, "Every student goes through, reversing the lockers which correspond to his or her position in line until the 1000th student has passed through", we felt this answer will get inverted, i.e. 2, 3, 5 Open, 1 and 4 Closed, which ksi had provided, and this was what we got also. Does this "inversion" make sense ?

Incidentally, most of the solutions on the Internet do not have this last sentence. I think the school added this sentence to introduce some variance to the question.

What do you all think ?