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Bunuel
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Hero8888
Smart guessing approach :

A (of trapezoid) = A (of rectangle) - A (triangle 1) - A (triangle 2)
Let a= 2, then A (of trapezoid) = 2*4 -1/2*2*4-1/2*2*1 = 3, where (1 - is estimated length, which lays in the range from 0 to 2)
Subsrituting with a=2 answer options

A 1
B 2
C 3 - closest, let's pick it.
D 6
E 8

This is not the best approach, but it works in most of the cases, when you have no clue how to solve the problem. You have to never give up.

I think this is a great approach, especially for individuals who are less comfortable with algebra. Good explanation.
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For those who are not well aware of the properties of the trapezoid this method might be a close approach
drop a perpendicular from q
therefore now we have to figure out the area of a triangle and rectangle
since the distance between q and r is a
therefore individual sides being a/2^1/2 for simplicity and approximation
area of rectangle being a^2/(2^1/2 )
total area equals 3a^2/2*(2^1/2) which is approximately C
This i think is just another brute force method might not work in Gmat
Thanks :)
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Hero8888
Smart guessing approach :

A (of trapezoid) = A (of rectangle) - A (triangle 1) - A (triangle 2)
Let a= 2, then A (of trapezoid) = 2*4 -1/2*2*4-1/2*2*1 = 3, where (1 - is estimated length, which lays in the range from 0 to 2)
Subsrituting with a=2 answer options

A 1
B 2
C 3 - closest, let's pick it.
D 6
E 8

This is not the best approach, but it works in most of the cases, when you have no clue how to solve the problem. You have to never give up.

You don't need to guess here. The approach is absolutely valid.
Note that we have a trapezoid which means PQ is parallel to OR.
The co-ordinates of R are (2a, a) which means for an increase of 2a in x, y increased by a i.e. half. So slope of OR is 1/2.
Then slope of PQ is 1/2 too. Since from P to Q, x co-ordinate increases by a, the y co-ordinate must have increased by a/2. So y co-ordinate of P must be a/2.
Then if a = 2, P is (0, 1), Q is (2, 2) and R is (4, 2).

A (of trapezoid) = A (of rectangle) - A (triangle 1) - A (triangle 2)
A (of trapezoid) = 4*2 - (1/2)*1*2 - (1/2) * 4*2 = 3

Put a = 2 in options to get 3 for option (C).
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Bunuel

Trapezoid OPQR has one vertex at the origin. What is the area of OPQR ?


A. \(\frac{a^2}{4}\)

B. \(\frac{a^2}{2}\)

C. \(\frac{3a^2}{4}\)

D. \(\frac{3a^2}{2}\)

E. \(2a^2\)


Like the majority of "difficult" geometry questions, we can deploy REASONING in lieu of getting all "quantitative." See my signature below.

Let's see if we can just use Ballparking.

The base of the red rectangle is \(2a\). The height is \(a\). The area is \(2a^2\).

Diagonal OR cuts the rectangle in half. The area of the top half is half the area of the entire rectangle, so the area of the top half is \(a^2\).

Look at the answer choices. They are all something multiplied by \(a^2\).

A. 1/4 of the top half? Nah.
B. 1/2 of the top half? Nah.
C. 3/4 of the top half? Maybe.
D. 1.5 times the top half? Nah.
E. The entire area of the rectangle. Nah.

Answer choice C.


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