Writing answers in "exact form"

Ive come across on papers when you have equations invloving ln(x) and e^x they ask to find solutions in exact form.

Do they mean leave the answer as e.g ln(3) or the the decimal version?

Would you get less marks if the answer is not in "exact form" (whatever exact form is?...i dont know)

Reply 1

christina.s

leave it as ln3....it basically means you dont have load of numbers written on your calculato which you'll have to do to 3dp/sf etc!....so examples are 10e or ln6

Reply 2

Ferchichi

Leave it in ln(3)

If you put in ln(3) and then carry on to give the decimals, even if you dont round it up, you dont get the final answer mark

:frown:

Reply 3

DFranklin

18

Catsvsdogs

Ive come across on papers when you have equations invloving ln(x) and e^x they ask to find solutions in exact form.

Do they mean leave the answer as e.g ln(3) or the the decimal version?

It means ln(3).

Would you get less marks if the answer is not in "exact form" (whatever exact form is?...i dont know)

I would think so, yes.

Reply 4

Kolya

17

ln(3) has a non-periodic decimal expansion, so writing it in some decimal version is always going to give an inaccurate value.

Reply 5

Catsvsdogs

OP

2

Thank you, you guys for clearing that up for me
It means i have lost many marks for a little mistake like that ...

Reply 6

Kolya

17

If you're worried about something you did in the past then I will say that, from marking some practice C2 papers, I know that they will drop a maximum of one mark for the mistake, and sometimes they don't penalize you at all (even if it did say "write the answer in exact form").

Reply 7

generalebriety

16

Lusus Naturae

If you're worried about something you did in the past then I will say that, from marking some practice C2 papers, I know that they will drop a maximum of one mark for the mistake, and sometimes they don't penalize you at all (even if it did say "write the answer in exact form").

One mark per question...

Reply 8

Kolya

17

generalebriety

One mark per question...

True, but the mark scheme doesn't penalize it all the time so I doubt they would lose more than 3 or 4 marks over an entire paper.

Reply 9

Cexy

But... but... that could be the difference between 93% and 98%, and if you get less than 98% you've basically failed!!

Reply 10

estel

18

Lol!

I usually just tried to get around it by writing = ln(3) = x.xxx

Hmm, another curiosity: the exam usually asks on the cover to give all *non-exact* answers to 3s.f. However, if the answer is exact to 8s.f., would the mark scheme expect 3s.f. or 8 s.f. ?

get good

Original post by estel

Lol!

I usually just tried to get around it by writing = ln(3) = x.xxx

Hmm, another curiosity: the exam usually asks on the cover to give all *non-exact* answers to 3s.f. However, if the answer is exact to 8s.f., would the mark scheme expect 3s.f. or 8 s.f. ?

If you are going to write a numbers decimal expansion out then just give it to 3sf or whatever they say on the front of the exam or something. You would never write an answer with like 7 decimal places because it's kind of ridiculous.

Writing answers in "exact form"

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