Basic Ratio Maths Prob help please am new

[Father Feck]

Hi i have a lack of understanding on ratios and would like help please? I done a test yesterday and one question was. Whats the ratio between 3 computers to 15 desks?

[Max Peck]

That would be 1 computer for every 5 desks.

A ratio is a simple division. x/y.

3 computers / 15 desks

reduces to

1 computer / 5 desks

-Max

[Father Feck]

Thanks Max so as you say i would show it as 1:5 so if the same question was 3 computers 76 desks the answer would be 76/3= 25:33?
or the correct way to calculate is the higher number divided by the lower then add so answer 3:25

[Max Peck]

Thanks Max so as you say i would show it as 1:5 so if the same question was 3 computers 76 desks the answer would be 76/3= 25:33?
or the correct way to calculate is the higher number divided by the lower then add so answer 3:25

Well, a ratio isn't strictly the higher-to-lower number, a ratio is just number-to-number. You can express it either way.

However, in this case you are wanting to express it as computers-per-desk which means the number of computers divided by the number of desks. So in the case of 3 computers and 76 desks you would get a ratio of 1 computer for every 25.33 desks.

I.E. 3/76 = 1/25.33

-Max

[jemidiah]

or the correct way to calculate is the higher number divided by the lower then add so answer 3:25

I'm not sure what you mean by this, but it sounds like you're doing magic with ratios. One way to explain a ratio is like this... you have two groups of things, in your question computers and desks. Take the smaller group (computers) and make piles with 1 item in each from that smaller group. Now try to distribute the larger group evenly into the piles you've started. In your example we would be in this situation now:

first pile: 1 computer 5 desks
second pile: 1 computer 5 desks
third pile: 1 computer 5 desks

What the ratio wants is the number of computers in each pile (which we've cut down to 1) compared with the number of desks in each pile (which turned out to be 5). Since the computers were the first group the 1 comes first and the 5 comes second, so the ratio of 3 computers to 15 desks is 1:5.

If you had added an extra desk for a total of 16 to this problem, you'd have to split it into 3 parts to distribute it to the piles evenly. You'd have this situation:

first pile: 1 computer 5 and 1/3 desks
second pile: 1 computer 5 and 1/3 desks
third pile: 1 computer 5 and 1/3 desks

Doing the same thing as before the ratio of 3 computers to 16 desks is 1:5 and 1/3 which is about the same as 1:5.33. You can probably catch the pattern at this point; we're just dividing the number of desks by the number of computers. The ratio of "x" computers to "y" desks is 1:y/x.

[Father Feck]

Thanks guys i understand now with your emails.