In a particular zoo, there are 20 apes evenly distributed between age 1 to 20. The annual mortality rate (qx) of the apes is 0.04x and is shown in the following table.

What is the probability that exactly 7 apes die in a year?

Age (x) qx No. of Apes
1 0.04 1
2 0.08 1
3 0.12 1
4 0.16 1
5 0.20 1
6 0.24 1
7 0.28 1
8 0.32 1
9 0.36 1
10 0.40 1
11 0.44 1
12 0.48 1
13 0.52 1
14 0.56 1
15 0.60 1
16 0.64 1
17 0.68 1
18 0.72 1
19 0.76 1
20 0.80 1

 

If you think you know the answer to the above brain teaser and you are our newsletter subscriber at 12 noon on 25 May 2013 (Competition Date), you stand a chance to win a cash prize of RM100. Please note that the Cutoff Time for this competition is 2 June 2013 16:00 (KL time).

Competition for the RM100 cash prize is now closed.  We have 9 qualified and correct entries.

The above brain teaser was only open to our newsletter subscribers as at 25 May 2013.

If you submitted an answer and your name does not appear on the Honour Roll, it is likely that you did not get the correct answer.

Based on the closing FBMKLCI as at 3 June 2013 of 1,766.33, we take 33 and divide by 9.  The remainder is 6, add 1 to 6 we get 7.

So the winner is "why".  Congratulations!

Instructions on how to claim your prize money will be emailed to you.  Please reply the email within 2 weeks, failing so the prize will be carried forward to the next competition.

Check your answer here.  Must first sign in to see.

  1. To submit your answer, use the submission form below.
  2. The email address you enter must match the one you used for our newsletter subscription (check your email to see where we sent our latest newsletter to).
  3. Your real name and email address will not be published to protect your privacy but it will be used by us to validate whether you are our newsletter subscriber on the Competition Date.
  4. Choose a unique nickname for us to publish in the Honour Roll in the event that your answer is correct.
  5. One winner will be chosen from the first 20 correct entries submitted before the Cutoff Time (see below for method of choosing the winner).
  6. The winner will walk away with RM100 cash.
  7. Please make sure your name as entered in the submission form matches the name you use in your bank account as the prize money will be transferred directly to your bank account and we are unable to pay you if the names do not match.
  8. Only 1 entry per person.  We reserve the right to disqualify you if we discover that you submit more than 1 entry using different email addresses.
  9. If no correct entry is received by the Cutoff Time, the first correct entry submitted after the Cutoff Time wins the cash reward.
  10. Winner will be announced on this page using the nickname.
  11. If case of dispute, our decision is final and binding.

The winner will be determined based on the closing FBMKLCI on the 1st trading day immediately after the Cutoff Time as follows:

  1. Take only the 2 digits after the decimal point, and lets say this 2-digit number is X.
  2. Divide X by N, where N is the number of correct entries by the Cutoff Time. Take the remainder and add 1.
  3. From the number obtained in Step 2, match it with the rank on the Honour Roll to decide the winner.
  4. The rank on the Honour Roll is determined based on the order of the submission of the correct entry.

As an illustration, assuming 11 correct entries and assuming that the closing FBMKLCI is 1,623.31:

  1. X is 31 based on the 2-digit number after the decimal point of closing FBMKLCI.
  2. Since there are 11 correct entries, N is 11.
  3. Divide 31 by 11 gives a remainder of 9.  Add 1 and we get 10.
  4. The 10th person on the Honour List is therefore the winner.
  5. Please note that by intention, this method may favour slightly those who submit their entries early.

Honour Roll

The following qualified newsletter subscribers submitted the correct answer (in the order of submission):

  1. lim yu wei
  2. yangster7
  3. Yap Chong Yong
  4. kokweng
  5. Yee Lee Ling
  6. misty
  7. why
  8. Chun Fei
  9. JHorng

Also see the all-time Top 10 Brain Teaser Solvers.

Modified 6/2/2013 by Loo Hai Teh

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