SMO 2017 Open Round 2 List
Cut off for Rd 2 ~13
SMO 2017 Open Questions
You can find past year SMO papers (2005-2013, Round 1 and 2 with full solutions) here.
SMO 2017 (Open Section) Answers
1. 3
2. 2
3. 4032
4. 11
5. 7
6. 7
7. 2017
8. 10
9. 10
10. 32
11. 43 (assuming solution exists)
12. 7
13. 45
14. 3
15. 1008
16. 2017
17. 4036
18. 35
19. 3
20. 45
21. 6
22. 121
23. 3025
24. 12
25. 28
q12 is 14?
ReplyDeleteq14 I got 2018
ReplyDeleteq8 i got 12
ReplyDeleteq22 I got 115
ReplyDeleteQ22 I got 121, filled the board with one color, then fit 6 new colors into each row, 6*20+1, the best I can do.
Deleteq19 i got 1
ReplyDeleteI think q19 should be 1 too.
Deletewhy isn't q8 14?
DeleteThis comment has been removed by the author.
ReplyDeleteq22 i got 106
ReplyDeleteq17 I got 2018
ReplyDeletewhy is q19 3 and not 8
ReplyDeleteApparently you have to mod 20 the numerator if you want to divide by 2.
Deleteq13 should be 60.
ReplyDeleteRearranging the given equation, we get a^2 = b(b-c)
If you construct a circle with centre at point A and with radius of c, you can directly apply the above equation to show that BC is tangent to the circle at B (by tangent-secant theorem). From there, x = 60 degrees.
@PSJH q13 should be 45.
DeleteYou can use cosine rule and sine rule to show (you should get sinC = 1/sqrt(2)) and C=135 deg is rejected
What do you think of this year's paper? Is it easier or more difficult that previous years?
ReplyDeleteqn 12 I got 17
ReplyDeleteand an 17 I got 8072? isn't it correct?
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ReplyDeleteFixing 1st term does not give unique way
Delete23. I got 3027
ReplyDeleteI got 3026...
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ReplyDelete@PSJH Q13 should be 45 not 60 just draw an accurate diagram
ReplyDeleteWhy do you think will be the cut-off for bronze?
ReplyDeletequestion 19 i got 8
ReplyDeleteunits digits of r = 2017^2017 = 7^2017 = 7^2016 * 7 = 1*7 = 7
ar = 7*8/2 = (2)8
You would need the last 2 digits of 2017^2017 to confirm the units digit. Thus, by finding the last 2 digits, which are 77, you get 77*78/2 = 3003 and 3 is the units digit.
ReplyDeleteFor question 19, you just need 2017^2017 mod 20, which comes out to 17 and is easier to generate. Furthermore, the pattern of a_n repeats after a cycle of 20 numbers.
ReplyDeleteyea what is the cut off for bronze and hm?
ReplyDeletewill 9 marks get me anything haha
ReplyDeleteBronze for 9 marks maybe. You'll probably need 14-15 marks to get silver and get into second round
ReplyDeleteIs 10 marks good enough to get something?
ReplyDeleteBy the way, I'm curious: how did you manage to supply all the correct answers within 1 hour after the paper ended anyway?
ReplyDeleteWe can bring home our paper and we probably had our answers recorded and the answers are provided by some math whiz so they should all be correct
ReplyDeleteq22 i got 134 by adding7*7+7*7+6*6
ReplyDeletehttp://sms.math.nus.edu.sg/Competitions/SMO2017/SMO%20Open%20R2.pdf
ReplyDeleteThe results are out! Anyone knows the cut off point?
I got 10 didn't get in
DeleteI got 12, didn't get in. My friend got 13 and got in.
ReplyDeleteI got 14 and got in.
ReplyDeleteI also got 12 and did not get in
ReplyDelete9 honorable mention
ReplyDelete10-12 bronze
13 silver
How did you know all these results?
DeleteWhy q4 is 11?
ReplyDeleteI have know... Sorry
DeleteQ11, there is no need to assume solution exists.
ReplyDeleteThe question said that all of a, b, c and d are positive.
You can therefore show all the quantities required during manipulations,
not only exist, but are positive.
Q4) Note that you are integrating the floor function of x. Since floor(x) = 0 for 0 < x < 1, integrating from 0 to 1 gives 0. Similarly, integrating from 1 to 2 gives 1. Integrating floor(x) from 0 to integer a gives 0 + 1 + ... + (a - 1). Solving, a = 11
ReplyDelete11) When Lim Jeck says "assuming solution exists", he means that it is one of those "flawed questions" where the scenario is impossible. For more examples of such questions, see SMO(J) 2014 Q26 or SMO(J) 2015 Q35.
The issue here is that if a, b, c, d are all positive and a + b + c + d = 8, then a / (b + c + d) + ... + d / (a + b + c) cannot be equal to 3/10 because the expression is naturally greater than 4/3.