The combined area of the two black squares is equal to 1000 square uni

Question

https://gmatclub.com/forum/download/file.php?id=16514 The combined area of the two black squares is equal to 1000 square units. A side of the larger black square is 8 units longer than a side of the smaller black square. What is the combined area of the two white rectangles in square units? (A) 928 (B) 936 (C) 948 (D) 968 (E) 972 Square.PNG Guys this is how I am trying to solve this: Let Side of smaller square be x Side of larger square will be x+8 Area of smaller square x^2 Area of larger square (x+8)^2 So the sum of the areas = 1000 which brings me to the equation x^2 +8x-468 . I don't think we an simplify this equation any further, well I can't and therefore need help.

Bunuel · Accepted Answer

https://gmatclub.com/forum/download/file.php?id=16514 The combined area of the two black squares is equal to 1000 square units. A side of the larger black square is 8 units longer than a side of the smaller black square. What is the combined area of the two white rectangles in square units? (A) 928 (B) 936 (C) 948 (D) 968 (E) 972 I guess the black squares are the red squares on the diagram. The length of a smaller square - x; The length of a larger square - x+8; The area of entire square - x^2+(x+8)^2=1000 --> 2x^2+16x=936; The combined area of the two white rectangles - x(x+8)+x(x+8)=2x^2+16x --> look up: 2x^2+16x=936. Answer: B. Square.PNG

anairamitch1804 · Answer

Assume the larger red square has a side of length x + 4 units and the smaller red square has a side of length x - 4 units. This satisfies the condition that the side length of the larger square is 8 more than that of the smaller square.

Therefore, the area of the larger square is (x + 4)2 or x^2 + 8x + 16. Likewise, the area of the smaller square is (x - 4)^2 or x^2 - 8x + 16. Set up the following equation to represent the combined area:

(x^2 + 8x +16) + (x^2 - 8x +16) = 1000
2x^2 + 32 = 1000
2x^2 = 968

It is possible, but not necessary, to solve for the variable x here.

The two white rectangles, which are congruent to each other, are each x + 4 units long and x - 4 units high. Therefore, the area of either rectangle is (x + 4)(x - 4), or x^2 - 16. Their combined area is 2(x^2 - 16), or 2x^2 - 32.

Since we know that 2x^2 = 968, the combined area of the two white rectangles is 968 - 32, or 936 square units. The correct answer is B.

atalpanditgmat · Answer

X^2 +26x- 18x-468=0 ie X=18 and X= -26.

Discard negative value thus X=18.

Hope it helps...

gultrage · Answer

Let smaller square be of side x then bigger square has a side of x+8
(x)^2 +(x+8)^2=1000
2x^2+8x-468=1000
(x+26)(x-18)=0
x=18
Now,the entire figure is a square of side 18+26=44
Total are=44^2=1936
White are=total area-coloured area=1936-1000=936

ButwhY · Answer

Let a be side of big square
b be side of small square
given a*a +b*b =1000
and a=8+b

so (8+b)^2+b^2=1000
on solving b = 18 and a=26

need to find total area of two rectangles given
we get 44^2-1000 = 936

Sol:B

ConnectTheDots · Answer

sum of area of black squares(1000) + sum of area of white rectangles(X) = area of the larger square (Y)

From the options, X is an integer, hence Y (= X + 1000) is an integer too.

As Y is a square number, From the properties of square numbers, Y can only end with 0,1,4,6,9 or 25.

From the given options, only B (ending 6) is a possible solution, as +1000 doesn't change unit digit value.
Number ending 2 or 8 + 1000 (as in all other options) can never be a square number.

Besides, all of the above ways are equally correct.

vaidhaichaturvedi · Answer

hi Any quick way to solve and get factor for x2+8x-468

grichagupta · Answer

I solved it in under 2 mins using the below approach:
Let X and x be the sides of big and small squares respectively.

X-x=8
X^2 +x^2= 1000
or (X-x)^2 +2Xx=1000
or 64 +2Xx= 1000
or 2Xx = 936

Now. area of the two white squares are Xx +Xx = 2Xx = 936

EMPOWERgmatRichC · Answer

Hi All,

If you don't see the 'elegant' approach to this question, then you can still solve it with some 'brute force' math (and a bunch of multiplication) - it's not 'pretty', but if you're comfortable doing math by hand then you can still get to the correct answer in 2 minutes:

We're told that the sum of two squares is 1000 and that the two numbers (before they are squared) differ by 8. Since the answer choices to the question are integers, it's likely that the two side lengths of the two squares are also integers. Let's list out some perfect squares and get a sense of how big the numbers can get...

20^2 = 400 
30^2 = 900

Since the larger square is clearly bigger, it's area will be more than half of the 1000, so it's side length will fall into the range of 20-30. The side length of the smaller triangle will be 8 LESS... Now let's try to narrow things down a bit...

15^2 = 225 
25^2 = 625 
17^2 = does NOT end in a 5, so there's no way the sum would be 1000, but this example probably isn't too far away from the correct answer...

26^2 = 676 
18^2 = 324

This IS the sum that we're looking for, so these MUST be the dimensions of the two squares. By extension, the dimensions of the two white rectangles are 26x18 and the area of each is 468. Since there are two of those rectangles, their total area = 468(2) = 936.

Final Answer:  B

GMAT assassins aren't born, they're made, 
Rich

MrJglass · Answer

How did you get "-468"?

Posted from my mobile device

generis · Answer

MrJglass  , welcome to GMAT club! That post was awhile ago, so getting an answer from the author is unlikely. I agree: (-468) in that post is confusing.

This equation is not self-evident, and seems to me to be insensible:
 2x^2+8x-468=1000

That said, "-468" comes from dividing one form of the equation by 2 and subtracting RHS from both sides.

Thus: 
 x^2 +(x+8)^2=1,000  ->

2x^2+16x+64=1,000 
Divide by 2, subtract 500 from both sides
 x^2+8x+32=500 
 x^2+8x-468=0

Hope that helps.

MrJglass · Answer

Yea, thanks!

Posted from my mobile device

Archit3110 · Answer

although a straight fwd question but time intensive because of calculations
given square 1 + square 2 area = 1000
so x^2+(x+8)^2=1000
solve for x we get 18 & -26 since -ve value wont be correct so x= 18 and other side of square = 18+8 ; 26
so rectangle white side area ; 18*26 * 2; 936 
IMO B

VT44 · Answer

The combined area of the two black squares is equal to 1000 square units. A side of the larger black square is 8 units longer than a side of the smaller black square. What is the combined area of the two white rectangles in square units?

(A) 928 
(B) 936 
(C) 948 
(D) 968 
(E) 972

Guys this is how I am trying to solve this:

Let

Side of smaller square be x
Side of larger square will be x+8

Area of smaller square   x^2  
Area of larger square   (x+8)^2

So the sum of the areas = 1000 which brings me to the equation  x^2 +8x-468 . I don't think we an simplify this equation any further, well I can't and therefore need help.

Hi,
Area of a square is side square.
Let The side of large square be x. 
X^2=1000+white rectangles. 
The answer has to be a square of some number - 1000. 
Simply look for an answer choice which has 1, 4, 9, 6, 5, 0 in the units place. 
The only Option with any of these digits is option B.

Hope this helps.

Posted from my mobile device

CrackverbalGMAT · Answer

Assume that the side of smaller square be   x  and the larger square be  x + 8.

Its given that  x^2 + (x+8)^2 = 1000

x^2 + x^2 + 16x + 64 = 1000

2x^2 + 16x = 936

If you try to solve this quadratic equation, it might take some time. So instead ,Let's try another approach.

length of the white rectangle =  x+8

width of the white rectangle =  x

Area of the white rectangle =  (x+8)*x

Area of the remaining 2 white rectangles =  2(( x+8)*x)  =  2x^2 + 16x = 936

Option B is the right answer.

Thanks,
  Clifin J Francis,
GMAT SME

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The combined area of the two black squares is equal to 1000 square uni

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The combined area of the two black squares is equal to 1000 square uni

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