Math Is Fun Forum

kymmy

Member

Registered: 2007-05-23

Posts: 4

ratio

Hi all, i'd love some help with this question, i think i have worked it out but it doesnt look right so im hoping someone can help or guide me.

I have a length of race track on my page that is drawn on a scale of 1:1000, the line is 67 millimetres long and i have to work out how long it would actually be using the scale.

Im a little stuck, ive been out of maths practice for a long time.

Also the question after that one says

Joe says "i can only measure the length on the diagram to the nearest millimetre",
This means he can only calculate the length of the actual track to the nearest.... A. mm  B. cm C. km and why is this so

Please help the penny drop

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: ratio

For most questions like this, to translate from a scale measurement to an actual one, you multiply by the right-hand number in the ratio, and divide by the left one, if it's something other than 1.

For example, if you were using a scale of 1:50 and measured a length of 15cm, then to get that into real length you would multiply by 50 (and divide by 1). 15 * 50 = 750cm = 7.5m.

However, in your case there's a shortcut. Your scale is 1:1000, and 'milli' basically means "a thousandth of a..."

So to multiply measurements in mm by 1000, you can just change the units into metres and you'll be done. So the length of the track is 67m, and Joe can only find the length of the actual track to the nearest metre. That answer isn't one of the options, which is a bit weird, but it's certainly right.

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Why did the vector cross the road?
It wanted to be normal.

kymmy

Member

Registered: 2007-05-23

Posts: 4

Re: ratio

thank you. i did have 67m but not sure how i got it plus it seemed short for a race track. And yeah meters isnt in the options for some reason, must be a trick. thanks again!