Geometry Qs - Rectangle with Diagonal

GRE Quant Problem Solving
1

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Hi, since this is a QC question shouldn’t we be skeptical about the diagonal dividing the rectangle into two triangles ? Only if the rectangle is a square then it divides the 90 degree angle as 45, 45. So my question is when can we safely assume that when a diagonal is drawn across a rectangle it divides each side angle into 45, 45.

I thought the answer would be (D) here since we are not sure if the rectangle is a square.

2

With the diagonal of a rectangle, you can find l^2 + b^2. With the area, you have lb. You can find l and b.

3

The answer is C clearly, with diagonal 10 units given.

4

Yeah I know it is C “clearly”, but I was asking for an explanation not the answer key