A Distorted Grid

Geometry Level 2

In this grid, each rectangle is labelled with its area. What area should replace the question mark?


The answer is 24.

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22 solutions

Tushar Kaurani
Sep 27, 2015

One way to solve this question is to find the common sides with another rectangles. For our rectangle, the rectangles with area 2 & 6 share a common height and width respectively.

So our answer will include But wait, multiplying 6 and 2 will also include height of R1 and width of C1. So divide the expression with their height and width, which can be done by putting 3 & 1 in the denominator i.e Now, our expression still contains height of R3 and width of C3 in the denominator, So multiply the expression with 3 & 4. . And finally notice that the expression still contains height of R2 and width of C2 in the numerator. So divide the expression by 2.

This is the most brilliant method, according to me! :) But I feel that you could've elaborated in the beginning, as where 3 and 1 came from. Of course, one look at the diagram tells us what's needed, but that's to those who have followed..

Vaibhav Shete - 5 years, 8 months ago

Don't get it. It is not all clear to me why I have to bother with the height of R3 and width of C3. Or why I divide by 2 (and how do I know that it's division?). Completely opaque to me, esp. after step 2

Rhys W Roark - 3 years, 2 months ago
Michael Fuller
Sep 24, 2015

Denote the columns of the grid from left to right C 1 , , C 4 { C }_{ 1 }, \dots , { C }_{ 4 } and the rows of the grid from down to up R 1 , , R 4 { R }_{ 1 }, \dots , { R }_{ 4 } .

Consider the rectangles in positions ( C 2 , R 2 ) \left( { C }_{ 2 },{ R }_{ 2 } \right) and ( C 3 , R 2 ) \left( { C }_{ 3 },{ R }_{ 2 } \right) . Since their heights are the same, we conclude C 3 = 2 C 2 { C }_{ 3 }=2{ C }_{ 2 } , therefore the rectangle in position ( C 3 , R 3 ) \left( { C }_{ 3 },{ R }_{ 3 } \right) has area 3 × 2 = 6 3 \times 2 = 6 .

Similarly, we find that 2 C 3 = C 4 2{ C }_{ 3 }={ C }_{ 4 } so the rectangle in position ( C 4 , R 3 ) \left( { C }_{ 4 },{ R }_{ 3 } \right) has area 6 × 2 = 12 6 \times 2 = 12 . Also we find that 2 R 3 = R 4 2{ R }_{ 3 }={ R }_{ 4 } , so the area of the rectangle in position ( C 4 , R 4 ) \left( { C }_{ 4 },{ R }_{ 4 } \right) is 12 × 2 = 24 12 \times 2 = \large \color{#20A900}{\boxed{24}} .

Why make it more complicated than is necessary? Just recognise the relationship between rows and use that to calculate the required area

Danny Shiraz - 5 years, 8 months ago

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It's just a way of visualising what I did in my head. If I just said the rectangle next to the 3 is 6, people may not understand what I'm doing.

Michael Fuller - 5 years, 8 months ago

just measure it - its not 24 . and the other areas are not valid either. regardless of what rectangle you choose to be the point of origin of these X numbered-arbitrary measurements . Dumb question

Joshua Coddington - 5 years, 8 months ago

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In geometry, you're not allowed to base answers off of the picture. Of course you have to get your information from it, but size and scale aren't accurate. The picture is simply there to give you an idea of what you're doing.

julien viernes - 5 years, 8 months ago

Ever heard of "NOT DRAWN TO SCALE"? Dumb person

Kevin Shi - 2 years, 2 months ago

Too good innovative question

vishwesh agrawal - 3 years, 9 months ago

Though dictation of the grids are little complicated to make out, I thank a lot.

Ritabrata Roy - 3 years, 9 months ago

RE: Since their heights are the same, we conclude C3 = 2C3 , therefore the rectangle in position (C3 R3) has area 3 x 2 = 6.
This seems like a huge leap to me from the "since" to the "therefore"--missing several steps to make this clear.

Rhys W Roark - 3 years, 2 months ago

Let the partitioned rectangle of area 1 1 have a width of x x units and a height of y y units. Then x y = 1. xy = 1.

Then since the top left area 2 2 rectangle has the same width as the area 1 1 rectangle, its height must be 2 y . 2y. This will also be the height of the rectangle marked "?".

Next, since the area 3 3 rectangle has the same height as the area 1 1 rectangle, its width must be 3 x . 3x. The area 2 2 rectangle below the area 3 3 rectangle then also has width 3 x , 3x, and so the area 4 4 rectangle must have width 6 x . 6x. The area 3 3 rectangle below the area 4 4 rectangle must then also have width 6 x , 6x, and so the area 6 6 rectangle has width 12 x . 12x. The "?" rectangle must then also have width 12 x . 12x.

The "?" rectangle thus has height 2 y , 2y, width 12 x , 12x, and area 12 x 2 y = 24 x y = 24 1 = 24 . 12x*2y = 24*xy = 24*1 = \boxed{24}.

(Note that the height of the whole rectangle is 2 y + y + 2 3 y + ( 3 4 ) ( 2 3 ) y = 25 6 y , 2y + y + \frac{2}{3}y + (\frac{3}{4})(\frac{2}{3})y = \frac{25}{6}y, and has an overall width of x + 3 x + 6 x + 12 x = 22 x . x + 3x + 6x + 12x = 22x. Its area is thus 22 x 25 6 y = 275 3 x y = 91.666.... 22x*\frac{25}{6}y = \frac{275}{3}xy = 91.666.... )

Beautiful solution

Amond Ngobeni - 4 years, 9 months ago

clumsy answer

MAINAK PHYSICS - 3 years, 10 months ago

this is the most intelligible of the 3 so far.

Rhys W Roark - 3 years, 2 months ago

The answer and the question provider may be the same person ... but whoever it is couldn't explain it properly ... include some basics and rules as well applied to your approach ...

Shovan Chowdhury - 3 years, 9 months ago

the factors of columns can be used

1 X 3 = 3 increased by 3 factors

2 X 2= 4 increased by 2 factors

3 X 2 = 6 increased by 2 factors

then

2 X 3 X 2 X 2 = 24

did the same - we have factors for pairs of columns and this covers all 4 columns so this was the simplest way to calculate.

Steven Linnell - 4 years, 2 months ago
Pooja Nath
Jan 15, 2016

Very simple solution:

Each adjacent rectangle has one side in common with the other. Starting from the top left-most corner and proceeding downwards and towards right, we can write the area of each rectangle as:

a*b = 2

b*c = 1

c*d =3

d*e = 2

e*f = 4

f*g = 3

g*h = 6

The missing block, with area a*h = 24

Last step is to multiply and divide all the equations mentioned above, such that you get. (a b)/(b c)=2 -->a c=2 Then you can similarly combine the rest of the equations till you find a h=24

Hunter Dixon - 4 years, 8 months ago
Kim Ian Macay
Jan 29, 2016

mao ni siya hahaah

right...i did the same way...

Rajat Pathak - 5 years, 1 month ago
Jonathan H
Jul 18, 2018

When we go across one column at a time, starting at two, we can take rectangles in the same row as each other to see how much wider the column to the right is than the one to the left. 3 is 3 times wider than 1, so we multiply the top left corner by 3 to get 6; 4 is 2 times wider than 2, so we multiply by 2 to get 12; 6 is 2 times wider than 3, so we multiply 12 by 2 to get 24, the top right corner.

Un Owen
Apr 16, 2018

Using the given areas of some squares, we can fill in the blanks from their relative proportions. Thus: From these squares, we can see that the top line goes from 2 to 6, or 3x, then 6 goes to 12, and, since 3 goes to 6 on the bottom right corner, we know that in the top right corner, 12 goes to 24, giving us our answer. ☺☺☺☺

Alkis Piskas
Oct 21, 2018

Let's name the horizontal sides a, b, c and d and the vertical ones e, f, g and h . We have the following 7 equations (horizontal size x vertical size = rectangle area): ae = 2, af = 1, bf = 3, bg = 2, cg = 4, ch = 3, dh = 6 . We need to find the area de . We start from the last equation: d = 6/h . We substitute h with it value from the previous equation and so on, going backwards. We get: d = 6/h = 6/(3/c) = 2c = 8/g = 8/(2/b) = 4b = 12/f = 12/(1/a) = 12a = 24/e. Hence de = 24 .

Edwin Gray
May 28, 2018

Ler a = the horizontal length of the upper left corner. Since the area = 2, the vertical length must be 2/a. This is enough information to work our way around the rectangle. We find the vertical lengths going down to be: 2/a,1/a, 2/3a,and 1/2a. The horizontal lengths from left to right are: a,3a, 6a, and 12a. We can use any known rectangle to deduce that a = 1. The dimensions of the ? square are 2/a x 12a. letting a =1, we get 24. Ed Gray

Ahsim Nreiziev
Mar 25, 2018

The easiest way is to compare the width of the columns to each other, as each columns fits a whole number of times into the one next to it.

The 2nd column is exactly 3x as wide as the 1st, due to the "1" and "3" rectangles in the second row having the same height, which means the difference in area must come from the width

Similarly, the "2" and "4" rectangles in the 3rd row show us [by virtue of being in the same row] that the 3rd column must be twice the width of the 2nd.

Finally, the "6" rectangle is obviously two of the "3" rectangle right next to it side by side, which must mean that the entirety of the last column is 2x the width of the 3rd column.

Thus, the right-most column is 3 x 2 x 2 = 12 times as wide as the left-most one, which means that the rectangle whose area we are being asked must have an area that's 12x the size of the left-most rectangle in that same row, of which we know the area. So that's 12 x 2 = 24 \large \color{#20A900}{\boxed{24}}

Robert Gill
Jan 2, 2018

From the second row, we know that the second column has three times the area as the first column. From the third row, the third column has twice the area of the second column and from the fourth row, the fourth column has twice the area as the third column. Therefore the square in question is 2 * 3 * 2 * 2 = 24.

Andryx Martinez
Dec 9, 2017

One way of solving it is by observing the relationship between numbers as they go up the rows on the grid.

Moving from 4th to 3rd: a 3 changes into a 4 (×4/3) Moving from 3rd to 2nd: a 2 changes into a 3 (×3/2) Moving from 2nd to 1st: a 1 changes into a 2 (×2)

Since the numbers are on the same grid, all the numbers must follow this multiplier rule when moving up the rows (they get divided instead when moving down).

Then, the 6 on the 4th row must be multiplied by 4/3, then 3/2 and lastly by 2 to get to the 1st row.

6 x 4/3 × 3/2 × 2 = 24!

Of course this also works by examining the columns instead as you go from left to right. Try it! :D

With the same line of reasoning, you'll end up with:

2 × 3 x 2 x 2 = 24!

Rishi Jayaram
Oct 29, 2017

Denote the rows of the grid from down to up R1, R2, R3 and R4 and the columns of the grid from left to right C1, C2, C3 and C4.

  • Let the width of (R1, C3) be w... [1]
  • Let the height of (R2, C2) be h... [2]

  • Width of (R2, C3) = Width of (R1, C3) = w

  • Height of (R2, C3) = Height of (R2, C2) = h

  • Area of (R2, C3) = Width of (R2, C3) * Height of (R2, C3)

  • w*h = 4... [3]

(R1, C4) has the same height as (R1, C3), but twice the area. Therefore, from [1] , the width of (R1, C4) = 2*w... [4]

(R3, C2) has the same width as (R2, C2), but 1.5 times the area. Therefore, from [2] , the height of (R3, C2) = 1.5*h... [5]

Height of (R3, C1) is the same as (R3, C2). Therefore, from [5] , the height of (R3, C1) = 1.5*h... [6]

(R4, C1) has the same width as (R3, C1), but twice the area. Therefore, from [6] , the height of (R4, C1) = twice the height of (R3, C1) = 2 (1.5 h) = 3*h... [7]

  • Width of (R4, C4) = Width of (R1, C4) = 2*w (From [4])
  • Height of (R4, C4) = Height of (R4, C1) = 3*h (From [7])
  • Area of (R4, C4) = Width of (R4, C4) * Height of (R4, C4) = (2 w) (3 h) = 6 w*h

But w h = 4 (From [3]) Therefore, Area of (R4, C4) = 6 (w h) = 6 (4) = 24

Samir Betmouni
Oct 26, 2017

You don't have to work out the height and width of the rectangles.

Those on the same row have the same height. So those in column three are twice as wide as those in column two. And those in column four are twice as wide as those in column three.

Sim: row three are 1.5 times as high as row two.

Above the 4 is a 6, then a 12. To the right of the 12 is a 24

Richard Harris
Jul 5, 2017

Simply ? = 2 * 3/2 * 4/3 * 6

(From the relationship between the rows from the given areas)

Affan Ahmad
Feb 7, 2017

Areas for marked rectangles are: ab=2; ac=1; cd=3; de=2; ef=4; fg=3; gh=6

and for the unknown area rectangles bh=Area of Unknown

eleminating all variables except "b"

a= 2 b \frac{2}{b} ; c= b 2 \frac{b}{2} ; d= 6 b \frac{6}{b} ; e= b 3 \frac{b}{3} ; f= 12 b \frac{12}{b} ; g= b 4 \frac{b}{4} ; h= 24 b \frac{24}{b}

Now substituting on last equation for unknown area b* 24 b \frac{24}{b} =Area of Unknown Area of Unknown=24

Michael McCauley
Dec 2, 2016

Take any four rectangles such that all rectangles occupy only two rows and two columns. We'll choose the middle 4 rectangles for this example. Since the area of a rectangle is base * height, we can see that if we multiple the top left rectangle's area with the area of the bottom right rectangle, we obtain an area equal to the top right rectangle's area times the bottom left rectangle's area.

              a    b
       c   ||A1||A2||
       d   ||A3||A4||

A1 = a * c, A2 = b * d, A3 = a * d, A4 = b * d
A1 A4 = A2 A3 = a * b * c * d

Namely, 3 * 4 = 2 * x where x is the area of rectangle above the rectangle with area 4. We get that x = 6. We can use this algorithm to solve for the area in the bottom right corner. We get that the area is .5 Now let A1 be the area of the top left rectangle, A2 be the area of the top right rectangle, A3 be the area of the bottom left rectangle, and A4 be the area of the bottom right rectangle. ||A1|| || ||A2|| || || || || || || || || || || ||A3|| || ||A4||

Now A1A4 = A2A3 2*6 = ? * .5 ? = 24

Eddie Brown
Aug 25, 2016

My Solution is probably less elegant than most. I walked the given areas to calculate the sides.

Given R3,C1 has area 1, both sides must be 1. Therefore, the height of R4,C1 is 2. That gives us the height of R4,C4.

Now, the width of R2,C3 has to be 3. since we know the height is 1.

Given a width of 3 and area of 2 for R2,C2, the height has to be 2/3

Given a height of 2/3 and an area of 4, the width of R2,C3 is 6

Given a width of 6 and an area of 2, the height of R1C3 is 1/2

Given a height of 1/2 and an area of 6, the width of R1,C4 is 12 which is also the width of R4,C4

2x12 = 24

Graham Hanchet
Sep 25, 2015

This could be a bit of a crude explanation but here goes...

So there were two ways I saw to do this using proportions only. I personally used the vertical way and so will explain that method. Because the ? is in the same column as the 6, we did not need to account for any horizontal change from there. Now if we assume the top row is R1 and continue down to the bottom at R4, we see that going from R1 to R2 means the area will half. From R2 to R3, it dropped a third. R3 to R4 dropped a quarter of the area.

Now to reverse that starting from 6:

6* 4/3 = 8

8* 3/2 = 12

12 * 2/1 = 24

And so area of ? is 24.

It may be a crude way, but works for these kind of problems.

First assume the rectangle whose area is 4 as a square. This means that it's each side is 2. Solve for breadths of adjacent rectangles and at last we get 6 as length and 4 as breadth for required rectangle. So, the area becomes 24.

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