You are Here: Home >< GCSEs

# Mathswatch watch

1. Question 3b page 3 (118C
2. (Original post by Official-21)
Question 3b page 3 (118C
Diameter = 12cm

Lowest multiple of 12 under 50 is 48
48 /12 = 4

Lowest multiple of 12 under 100 is 96
96 / 12 = 18

4 CDs can be cut across the height, 8 CDs can be cut across the width.

Hence 8 x 4 = 32 CDs can be cut. This is assuming you are allowed to waste extra plastic or stick 2 pieces together in some way.

Diagram on next comment.
3. Why cant you just do area of rectangle devided by area of circle
4. (Original post by Official-21)
Why cant you just do area of rectangle devided by area of circle
Because once you cut out the 32 CDs, the remaining plastic will not be round. In order cut out more CDs, you would need to stick pieces of plastic together which the question doesn't say you can do.
5. where did you get 32 cd's from
6. (Original post by Official-21)
where did you get 32 cd's from
The diameter of the circle is 12cm. This means the smallest bit of square plastic you can cut a CD from is 12cm x 12cm.

4 CDs can fit the height (50cm) of the plastic with 2 cm left over.
8 CDs can fit the width (100cm) of the plastic with 4 cm left over.
4 (in height) x 8 (in width) = 32 CDs.

The remainder of the card would not be big enough to cut out CDs from. You cannot cut more circles as you cannot stick 2 pieces of plastic together to make a CD.

Area circle = (6^2) x pi = 36pi
Area of plastic sheet = 50cm x 100cm = 5000 cm^2
5000 / 36pi = 44.21 (2dp)
32 CDs could be cut, but 44 CDs could be cut if you could stick plastic together to make a CD.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: March 4, 2018
Today on TSR

### He broke up with me because of long distance

Now I'm moving to his city

### University open days

1. Norwich University of the Arts
Thu, 19 Jul '18
2. University of Sunderland
Thu, 19 Jul '18
3. Plymouth College of Art
Thu, 19 Jul '18
Poll
Useful resources

## Study tools

### Essay expert

Learn to write like a pro with our ultimate essay guide.

See where you can apply with our uni match tool

### Make study resources

Create all the resources you need to get the grades.

### Create your own Study Plan

Organise all your homework and exams so you never miss another deadline.

### Resources by subject

From flashcards to mind maps; there's everything you need for all of your GCSE subjects.

### Find past papers

100s of GCSE past papers for all your subjects at your fingertips.