Working out for numerical questions (1 Viewer)

[emilios]

Hey guys.

I can understand that for 'Show' or 'Prove' q's you'd have to provide full working out. However I've heard that if the final answer required is a specific value, you attain full marks for just stating that value.

For example, in all those partial fractions decomposition questions, I never do the whole "cross multiply, collect like terms and collect coefficients" thing, and if I do, my working out for that won't be very structured. If I still find the correct value of the constants e.g. if I just state A=2 , B=1, C= 4 , would I still attain full marks?

Another thing:
I just did a question that required me to find

Integral (between 0 and pi/2) for sinx/(1+cos^2(x)) dx . I spotted this to be of the inverse tan form and transformed the boundaries in my head, giving me the correct answer of pi/4. Would I still be required to show all the tedious working out though (let u=cosx and change boundaries) or would I get the full 3 marks for just stating the correct answer?

 

[faisalabdul16]

You have to show full working out. Even for some 1 marker questions like the limits type ones, you have to show how you got your answer (some markers are harsh). Despite some answers naturally coming to head because of the easiness, you have to show working out because specific steps are given marks and that's how you get your marks.

Show full working out for all questions

 

[Kurosaki]

Well it does say on the front of the paper to show relevant reasoning and calculations

 

[aDimitri]

i usually just write "by inspection" for the partial fractions qs...

 

[Carrotsticks]

i usually just write "by inspection" for the partial fractions qs...

 

[Carrotsticks]

Hey guys.

I can understand that for 'Show' or 'Prove' q's you'd have to provide full working out. However I've heard that if the final answer required is a specific value, you attain full marks for just stating that value.

For example, in all those partial fractions decomposition questions, I never do the whole "cross multiply, collect like terms and collect coefficients" thing, and if I do, my working out for that won't be very structured. If I still find the correct value of the constants e.g. if I just state A=2 , B=1, C= 4 , would I still attain full marks?

Another thing:
I just did a question that required me to find

Integral (between 0 and pi/2) for sinx/(1+cos^2(x)) dx . I spotted this to be of the inverse tan form and transformed the boundaries in my head, giving me the correct answer of pi/4. Would I still be required to show all the tedious working out though (let u=cosx and change boundaries) or would I get the full 3 marks for just stating the correct answer?

You should attain full marks for writing down the correct values. In the marking criteria for partial fraction problems, the first mark is for attempting partial fraction decomposition. The second mark is for acquiring the correct partial fraction decomposition and the third is for acquiring the correct primitive (they are usually 3 marks for indefinite integrals).

Notice that no marks are awarded for the actual steps in partial fraction decomposition. By writing down the correct values, you have already acquired 2 marks.

Regarding your second question, I am not completely sure (I doubt you would get all of 3 marks) because the HSC in the past have been a bit iffy about simply writing down the answer. For example, in 2009 HSC Question 3 (f), you had to find the square roots of 3+4i. They explicitly said in the markers comments that candidates who simply wrote down the answer (even if correct) were not awarded full marks.

If I were you, I would write down the transformed primitive at least, and then write down the answer by inspection.

 

[mreditor16]

Well it does say on the front of the paper to show relevant reasoning and calculations

lol'd at the smart-ass comment

lol'd even more

 

[aDimitri]

that's not a partial fractions Q, you can just do common denominators.
i was obviously referring to "Find integers A & B such that..."