mathsmathsmaths +rep

[MattFr]

you can't no, but i left out changing 13.1/99 to 131/990 because it seemed kinda needless... but yeah i've been taught that aswell

It's not pointless considering 13.1/99 would get you no marks

[kk.]

ive been taught you can't have a decimal in a fraction?

its how you left it anyway.. but no, you shouldnt have decimals in fractions.

[alexxxxx]

ive never been taught this and i do a-level maths :S

it's not like it really matters all that much anyway.

[kk.]

ive never been taught this and i do a-level maths :S

it's not like it really matters all that much anyway.

ive never had to use it in a level maths , nor on further maths lol

[Soka]

for ones such as 0.1313131313 your method is correct... let x = 0.1313..., then 100x = 13.13... so 99x = 13, there x = 13/99
the key is to make sure you multiply x by the period (size) of the recurring part. so in above case 0.131313 obviously has repeating period 2 (as 13 is two digits). so you'd mutiply by 10^2 = 100. if it was 0.134134134, you'd multiply by 10^3 = 1000, then 999x.. then x=134/999.

for the other one x = 0.132323232, where you have a non-recurring part at the beginning first multiply by 10^n where n is the period of the non recurring part.. so in this case it is period 1 (1 has one digit)... so 10x = 1.32.... then carry on same as previous part.. so multiply this by 10^2 = 100.. so 1000x = 132.32...
then we can say 990x = 131, then x = 131/990, as a fraction.

i think alot of the guys above where missing out the step in bold.. so was not getting a fraction as the first answer ! so they had the right answer from multiplying 13.1/99 by 10, but this isn't the correct method and i don't think you'd get the marks... although i don't know at GCSE/A Level you might.
hope this helps if it makes sense.

[Matthew]

It's not pointless considering 13.1/99 would get you no marks

what i meant is that i assumed he would change the fraction to 131/990 himself

[Matthew]

for ones such as 0.1313131313 your method is correct... let x = 0.1313..., then 100x = 13.13... so 99x = 13, there x = 13/99
the key is to make sure you multiply x by the period (size) of the recurring part. so in above case 0.131313 obviously has repeating period 2 (as 13 is two digits). so you'd mutiply by 10^2 = 100. if it was 0.134134134, you'd multiply by 10^3 = 1000, then 999x.. then x=134/999.

for the other one x = 0.132323232, where you have a non-recurring part at the beginning first multiply by 10^n where n is the period of the non recurring part.. so in this case it is period 1 (1 has one digit)... so 10x = 1.32.... then carry on same as previous part.. so multiply this by 10^2 = 100.. so 1000x = 132.32...
then we can say 990x = 131, then x = 131/990, as a fraction.

i think alot of the guys above where missing out the step in bold.. so was not getting a fraction as the first answer ! so they had the right answer from multiplying 13.1/99 by 10, but this isn't the correct method and i don't think you'd get the marks... although i don't know at GCSE/A Level you might.
hope this helps if it makes sense.

its exactly how ive been taught at a GCSE level, so yeah im not sure for A level

what ive been taught is that you multiply it by 10x(the number of recurring numbers there are). so in 0.13232 there are 2 recurring decimals, therefore we times it by 100



EDIT: sorry for double post, it didnt occur to me at the time.

Edited by Okapia (Forum Moderator) Please try to avoid double posting within the 15 minutes editing time. Thanks!