# Perms and Coms question (1 Viewer)

#### MichelleW

##### New Member
Hi I need help with a question from the Cambridge 2u textbook (EX1C 13)
A piece of paper 0.01mm thick is folded successively 100 times. How thick is it now?

Most of the questions were alright but this one really stumped me.
Any help would be great.

##### Well-Known Member
I think this is a geometric series question - you just need to put stuff into the formula

#### B1andB2

##### Well-Known Member
usually with the folding qs you can just do 2^(how many folds) x thickness

= 2^100 x 0.01 in your case

are you sure you typed the q correctly? Because in the textbook it says 0.1 mm thickness lol

##### Well-Known Member
arn^n-1

0.02x2^99

I think it's this because the first time you fold it it doubles so a is 0.02 instead of 0.01. I might wrong tho

#### B1andB2

##### Well-Known Member
arn^n-1

0.02x2^99

I think it's this because the first time you fold it it doubles so a is 0.02 instead of 0.01. I might wrong tho
do you have to use that weird formula?

because it yields the same answer as 2^100 x 0.01

#### mmmm.

##### Active Member

PS: The question says 0.1mm not 0.01mm as OP said

#### beetree1

##### Well-Known Member
anyways any piece of paper cannot be folded more than 7times therefore the question is bull

#### MichelleW

##### New Member
usually with the folding qs you can just do 2^(how many folds) x thickness

= 2^100 x 0.01 in your case

are you sure you typed the q correctly? Because in the textbook it says 0.1 mm thickness lol
Yep my bad meant to type 0.1mm lol

Last edited:

#### MichelleW

##### New Member
Thanks for all the help I got it now

#### CM_Tutor

##### Moderator
Moderator
Hi I need help with a question from the Cambridge 2u textbook (EX1C 13)
A piece of paper 0.01mm thick is folded successively 100 times. How thick is it now?

Most of the questions were alright but this one really stumped me.
Any help would be great.
I'm tempted to say that the piece of paper's thickness has not changed. The stack of folded paper is much thicker than was the single, unfolded, sheet... but the single sheet remains the same thickness no matter how many times you fold it....