# Maths Calculator Ratio Question!!!!

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I know the answers 36:37 but I just don't understand how to get the answer! Could someone please help x Thanks

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

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#3

(Original post by

I know the answers 36:37 but I just don't understand how to get the answer! Could someone please help x Thanks

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

**gcsestudyblr**)I know the answers 36:37 but I just don't understand how to get the answer! Could someone please help x Thanks

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

2. What have

**you**tried? Please show us some working and/or thoughts of your own, thanks!

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#4

I would do it as using the values in that ratio in the question per 20 degrees sector. Do ask if what I said is weird because I'm awful at explaining things initially.

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(Original post by

1. Moved to maths.

2. What have

**Zacken**)1. Moved to maths.

2. What have

**you**tried? Please show us some working and/or thoughts of your own, thanks!
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#6

**gcsestudyblr**)

I know the answers 36:37 but I just don't understand how to get the answer! Could someone please help x Thanks

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

Area B is of plastic and of metal.

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#8

(Original post by

Don't need area to work it out. Just need to apply the cost ratio to the angles.

**Vikingninja**)Don't need area to work it out. Just need to apply the cost ratio to the angles.

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#9

(Original post by

Well, yeah, you get lucky here because they're both of the same radii and hence their angles are proportional to their area. But can you note that the ratio is specified in cm^2?

**Zacken**)Well, yeah, you get lucky here because they're both of the same radii and hence their angles are proportional to their area. But can you note that the ratio is specified in cm^2?

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#10

**gcsestudyblr**)

I know the answers 36:37 but I just don't understand how to get the answer! Could someone please help x Thanks

Question:

There are two watch faces, A and B.

Both watch faces are circular with radius 2cm. The materials used to make both watch faces have the same thickness. A is made entirely of plastic. B has a 20° sector of metal and a 340° sector of plastic. The ratio of the cost per cm2 of the metal to the cost per cm2 of the plastic is 3:2 Work out the ratio of the cost of the materials for A to the cost of the materials for B. Give your answer in its simplest form.

Think how many units each disc costs. Disc A has 360 plastic pieces, so it costs 360 x 1 = 360 units. Disc B has 340 plastic pieces, and 20 metal pieces, so it costs (340 x 1) + (20 x 1.5) = 340 + 30 = 370 units. Thus the ratio of the cost of A to the cost of B is 360:370 which can be simplified to 36:37.

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(Original post by

Imagine splitting each disc up into 360 equal pieces, with each piece spanning 1°. Let's say a piece made of plastic has a cost of 1 unit. By the ratio given, this means a piece the same size made of metal costs 1.5 units.

Think how many units each disc costs. Disc A has 360 plastic pieces, so it costs 360 x 1 = 360 units. Disc B has 340 plastic pieces, and 20 metal pieces, so it costs (340 x 1) + (20 x 1.5) = 340 + 30 = 370 units. Thus the ratio of the cost of A to the cost of B is 360:370 which can be simplified to 36:37.

**TimGB**)Imagine splitting each disc up into 360 equal pieces, with each piece spanning 1°. Let's say a piece made of plastic has a cost of 1 unit. By the ratio given, this means a piece the same size made of metal costs 1.5 units.

Think how many units each disc costs. Disc A has 360 plastic pieces, so it costs 360 x 1 = 360 units. Disc B has 340 plastic pieces, and 20 metal pieces, so it costs (340 x 1) + (20 x 1.5) = 340 + 30 = 370 units. Thus the ratio of the cost of A to the cost of B is 360:370 which can be simplified to 36:37.

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