Square ABCD

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by [email protected] » Wed Feb 17, 2016 10:36 am
Hi didieravoaka,

You should have posted this in the DS Forum, but I'll still help you walk through it.

We're told that a square has an area of 9, so we know its sides all equal 3. We're told two opposite sides of the square are lengthened. We're asked how much they're lengthened.

1) The diagonal of the resulting rectangle is 5.

With this Fact, we'll have a rectangle with a side of 3, a side of X and a diagonal of 5. Since the diagonal 'cuts' the rectangle into two right triangles, we can determine the value of X - we'll have a 3/4/5 right triangle, so X MUST be 4 and the two side lengths were each lengthened by 1.
Fact 1 is SUFFICIENT

2) The resulting rectangle can be cut into three rectangles of equal size.

It's important to keep in mind that this Fact does NOT state that the dimensions of those 3 rectangles have to be integers nor does it tell us how we're supposed to 'cut' the rectangle (lengthwise or widthwise).

For example, draw a rectangle that is 3x4 and another that is 3x6. Now cut each of those rectangles into 3 smaller, equal rectangles. You'll see that each rectangle can be cut in two possible ways and that there's more than one possible end result, so the increase in side lengths can be any value.
Fact 2 is INSUFFICIENT

Final Answer: A

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by didieravoaka » Wed Feb 17, 2016 5:42 pm
Thanks Rich. Oh I'm sorry I didn't pay attention to that before posting the question.

I'm still confused about something. Since we know that the area is 9, meaning all the sides are 3 inches each... Why do we have to consider two sides as x, such that x is not 3. To me, since the area of the square is 9 all the sides have to be 3 inches each.

Thanks to explain.

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by [email protected] » Wed Feb 17, 2016 8:35 pm
Hi didieravoaka,

The prompt tells us that we START with a square, but that two sides (AD and BC) are LENGTHENED to X inches each. Once that happens, we have a rectangle (with sides of 3 and X).

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