Math Is Fun Forum

nogdatmths

Member

Registered: 2005-09-10

Posts: 8

investigation---area--

hi guys
im stuck on a question on my work sheet.. now the answer is in the back of the worksheet as these r just practice ones.. but i dont want to write the answer because ive seen it i want to write the answer how i figured it out.. and i really dont no how to figure it out.. the question before the one im stuck on is....

draw as many rectangles as you can with an area of 25cm(2).why is there  a square this time? what other areas would  have a square as a possible solution? which has the smallest perimeter?

my answer was the width 5cm... the lenght 5cm... times 5 by 5 gives you 25cm(2)

and 25 can only be a square as you can only times 25 in the 5 times table.. so my next question is this.....

this time dont draw, just list-perhaps in a table- the lenght and width of as many rectangles as you can which have an area of 36cm(2) . which has the smallest perimeter? why should this be?

i owuld be so gratefull if some one can explain this to me as easy has ever as im still all new on the maths subjects.. thank you xxxxxxx

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sighned from  meeeeeeeeeeeeeeeeee

ryos

Member

Registered: 2005-08-04

Posts: 394

Re: investigation---area--

I assume they mean that only whole numbers are allowed (they should have said so!).

You can solve these by writing a factor table, like this:
1    2    3   4  6
36  18  12  9  6

These are all the factors of 36. This means, "Multiply the top number by the bottom number, and you'll get 36." Since you find the area of a rectangle by multiplying the length by the width, then these factor pairs are also your rectangles.

Good luck!

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El que pega primero pega dos veces.