Area Ratios

[flywithme]

just wondering if someone can explain to me where i went wrong with this question:


Clarence is painting a toy car which is identical in shape to his father's actual car. His car, however, is only 24 cm long whereas the actual car is 3.6m in length. He wants the toy car to be the same colour as his father's car and discovers that 500 cm squared is the area of his model that requires painting. The area of the actual car requiring the paint would be:

a) 750cm squared     b) 0.75 m squared   c) 75 m squared   d)11.25 m squared   e) 1125 m squared

So my working out went something like this:

3.6 / 0.24 = 15 so the length ratio is 1: 15.

Area Ratio = 1 squared : 15 squared
                = 1 : 225

225 x 500 cm = 112500 cm squared

112500 cm squared / 1000 = 1125 m squared, and so i arrived at the answer E.

HOWEVER the answer says d) 11.25 m squared.

anyone that can help, please do and thanks for bothering =]

[Collin Li]

225 x 500 cm = 112500 cm squared

112500 cm squared / 1000 = 112.5 m squared

You've got it all right except at the final step:

You should be dividing by 10,000 (100^2) to get from cm^2 into m^2.

[flywithme]

ahh of course, thanks.

time to write a conversion table in my book just in case

[Odette]

You need to divide by 10000 not 1000, because its 100 squared which is 10000...

 :oops: Coblin got to it first

It's my forum not yours lol ... kidding =]

[Collin Li]

It's my forum not yours lol ... kidding =]

Hehehe, competition. It makes it harder for us, but better for everyone else

[Odette]

Hehehe, competition. It makes it harder for us, but better for everyone else

Oh it's on lol they're my further maths students not your's lol