Forums › Ask ACCA Tutor Forums › Ask the Tutor ACCA PM Exams › Learning curve again…

- This topic has 3 replies, 2 voices, and was last updated 9 years ago by John Moffat.

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- November 2, 2014 at 9:31 am #207198
Hi John

Desperately need some help I’m afraid. Very similar query to the last question raised but I’m stumped I’m afraid and it’s now hindering revision!

Question in the Kaplan revision kit states first batch took 50 hours to make. The total time for the first 16 batches was 5,731 hours. What is the learning rate.

A 85%

B 90%

C 92%

D 94%I’m fine finding the answer by testing all of the occurrences above and keep repeating in a calculator but this is long winded and inefficient and will take up unnecessary time in the exam. I appreciate there must be a square root work back in here someone but the answer in the back also doesn’t really provide me with any greater clarity and I’d really like to be able this sort of question with great confidence (and speed) should it arise as it’s firmly stumped me at present. If in the exam one comes with first 256 batches for example, I’m going to be tapping away for 15 mins on a 1.8 minute question!!

Your assistance is greatly appreciated.

Kind Regards

Chris

November 2, 2014 at 10:57 am #207224Either you have mistyped the question or Kaplan has got a typing error, because the average time per batch when we make 16 is 5731/16 = 358 hours, which would be impossible since the first one only took 50 hours!

Apart from that, it really does not take long because each time we double, the average time is multiplied by r, where r is the learning rate,

If the rate is r,

if we make 2, the average time is 50 x r

if we make 4 then it is 50 x r^2

for 8 it is 50 x r^3

for 16 it is 50 x r^4(In the exam you don’t need to write that down, you can count in your head!)

So 50 x r^4 = the average time when we make 16.

r = fourth root of this, and the fourth root is simply the square root twice.

The examiner is not silly, and I doubt she will even go as far as 16 if she sets one of these questions.

November 2, 2014 at 11:16 am #207225Apologies John – first unit should have stated it took 500 hours.

November 2, 2014 at 12:42 pm #207239🙂

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