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Subscriber comments
- Hi, Tim,Yes I noticed that! I was wondering if I was missing something in the way of thinking. Got it.Thanks so much.Best wishes,Jason
- Hi Jason, Thanks for spotting that 'typo' error. All the working is correct - and finds the correct answer for the probability that the sum is 9 - but the text preceding the working should be P(sum=9), not P(sum=3). I'll fix it and post a corrected...
- Hi, Tim! I have another question for clarification from the same problem/paper, but this time Q.1 (b) (iii) (the one before the one I asked about above).Why is P(sum = 3) in the mark scheme when the probability of the sum of 9 is what is being...
- Hi, Tim! That makes a lot of sense by definition of median and not the list itself.Best wishes,Jason
- Hi Jason, Thanks for your query about Q.1 (b) (iv) on the HL P3 MockC. For a set of three numbers the median will be the number in the middle position when the numbers are listed in numerical order (ascending or descending). So, for your example...
- Hi, Tim!About P3 Mock C 2023#1(b)(iv) Is The mark scheme indicates that the ways for the median to be 1 are 1-1-2, 1-1-5, etc. but does this account for an arrangement such as 5-1-2 where the first and last numbers are different? By the...
- Hi Stephen, Thank you for your feedback on Q.2 in HL P3 MockE Exam. It is quite a challenge to write a suitable Paper 3 exam question. As stated in the Teacher Support Material (TSM), a P3 question should be “… a more exploratory type of...
- Sorry ignore my comment about correction
- Also the solution to the final question (e) (ii) should be an = n2 - n, not an =n2 + n
- Hi Tim, In HL Paper 3 mock exam E. Question 2 (e) (i) clearly requires students to have a very good working knowledge of the spreadsheet capabilities of their GDC. I would question if this is generally the case. What is your view regarding...
- Hi Tim, thanks for your answer. My point was that in calculating an angle one would use equation cosA=|a b / (|a| |b|) |. In this case the other soution (a=0) would also hold. And in this case we would obtain vector (1,0,-1) whose angle...
- Hi Barbara, Thanks for your comment about Q.3, part (d) on Test1 HL Vectors. Not sure I'm interpreting your comment corectly. There actually is no angle calculation because it is given that the angle between the plane and line L3 is 30 degrees;...
- Dear Tim, regarding solution a=0 problem 3d, Test # 1, you are right it is not the solution to equation 1/2 = (a-1)/sqrt(2aa + 4), but shouldn't there be an absolute value when calculating the angle beetwen a line and a plane to ensure an acute...
- Hi Vipul, Thank you for pointing this out. The exercise set with integration exam-like questions should not have been categorized as suitable for SL because - as you stated - solids of revolution are not in the SL syllabus. I have re-categorized...
- Hi, For AA_SL_5.10_integration_exam like questions, there is a question on volume of solid revolution. However, this is no longer on the syllabus.
- Hi Tim, that helps massively, thank you.
- Hi Ben, Good question. The short answer is 'no'. SL students only need to apply integration by substitution when the integrand is of the form stated in the syllabus - that is, where part of the integrand is the derivative of another part of...
- Hi Tim. If the students are required to integrate sqrt(a^2 - x^2) are they supposed to know that they should use the substitution x = a sin(theta)?Thanks
- Hi Prudence, The instructions to examiners on markschemes states that "Unless the question specifies otherwise, accept equivalent forms." So, if a question does not specifically state what units must be given for an angle then degrees or radians...
- Hi, may I ask whether students must answer questions involving angles using degrees as the standard unit (if no hint is given on the question)? Students ask me whether they can answer in radians but answer keys often indicate angles in degrees. Thank...
- Hi Ashley, Thanks very much for the helpful feedback. Yes, the instructions for Q.2 part (c) on HL Review Test 2 should have asked for the value of cos(75), not cos(15). I've corrected that. Thanks, Tim
- Hi Tim,Thank you for these. I think that HL Review Test 2, question 2c should say cos(75) rather than cos(15) - based on the solution.Thanks!
- Thank you! I will check that out.
- Hi Alexandra, The solution of a=0 does not work in the original equation 1/2=(a-1)/[√2√(a²+2)]. Substituting 0 for a gives 1/2=−1/2. Sorry, I should have explicitly stated in the worked solutions why a=0 was an extraneous solution. Cheers,...
- Test #1 for HLQuestion #3d- why a=0 is an extraneous solution?
- Hi Stephanie. You are correct. The solution set for #9 on SL Review Test 2 should include -9 since the inequality was < or =. Thank you for this very helpful feedback. I have corrected the answer and posted a new version (v2) of the worked...
- Hi Tim,Thanks for these review tests. I was using the SL review test 2 yesterday and I think #9 has an error in the key (should be < or = to -9?)
- Hi Varia. Thanks for pointing this out. The worked solution for MockE HL P3 Q.2 (b)(i) have incorrect values in the 2nd column for un. I made an error by starting the sequence with n = 0 (rather than n = 1) so each of my values should be one...
- Hi Tim,I am looking at P3 2024 Mock E HL Question 2bi.Using Recursion on GDC, your table implies that when n = 1, u1 = 1. But u1 = (1 + 11/2)1/2, so 21/2 = 1.4142. What am I missing?Varia