Animals on Scales

Algebra Level 1

Find the total weight of the three animals.


The answer is 27.

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25 solutions

Jádson Bráz
Jul 22, 2015

Suppose the weight of the cat be x x , weight of the rabbit be y y and weight of the dog be z z :

Hence according to the given figure,

( x + y ) + ( y + z ) + ( x + z ) = 10 + 20 + 24 (x+y)+(y+z)+(x+z)=10+20+24

2 x + 2 y + 2 z = 54 \Rightarrow 2x+2y+2z=54

2 ( x + y + z ) = 54 \Rightarrow 2(x+y+z)=54

x + y + z = 27 \Rightarrow x+y+z=27 .

Hence the total weight of all the three animals is 27 kg. \square

C+R=10, D+R=20, C+D=24. So... C+D+2R=30, therefore 2R=6 so R=3. C+D+3=27. Not quite to aesthetically pleasing as yours.

Craig Schofield - 5 years, 2 months ago

instead of this I have a special and simple trick we can just add all the three weights. this will become 2 animals each so we will just divide the total weight by 2 that is 54 divided by 2 will give answer 27.

prakhar mishra - 4 years, 12 months ago

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That's what this says lol

Qahir Mujaimin - 4 years, 5 months ago

O thats wonderful solution

Kamran Dawood - 5 years, 2 months ago

I used matrix and elementar transformations: 1 1 0 10 1 1 0 10
0 1 1 20 ~ 1 2 1 30 1 0 1 24 1 1 1 27

Aset Muratuly - 2 years, 5 months ago

Really helpful

Vinod Naik - 2 years, 2 months ago
Fahad Bin Alamgir
Jul 24, 2015

x=(weight of cat); y=(weight of rabbit); z=(weight of dog)

From the figure,

x+y=10

z+y=20

x+z=24

Adding,

(x+y)+(z+y)+(x+z)=10+20+24

2x+2y+2z=54

2(x+y+z)=54

x+y+7=27

i.e (weight of cat)+(weight of rabbit)+(weight of dog)=27

There is a small mistype, in the end it should be x+y+z=27

Gurmeet Singh - 3 years, 1 month ago

x > 2 is of course: 5 < x + x^2 8! so. 28 - 1 = 28. i.e. 27 + 1 = 28.

Am Kemplin - 1 month, 2 weeks ago
Sean Jargon
Jul 25, 2015

Apparently, I took the less beaten path of finding each animal's weight... the other solution is way simpler, but still, here it is.

  • b + c = 10
  • b + d = 20
  • c + d = 24

First thing to notice is that comparing the weigh-ins with the dog, the cat weighs 4 kg more than the bunny, so...

  • c = b + 4
  • plug it in to the first equation
  • 2b + 4 = 10
  • -4 on both sides
  • 2b = 6
  • /2
  • b = 3
  • plug it back in to the first equation
  • 3 + c = 10
  • -3
  • c = 7
  • 3 + d =20
  • 7 + d = 24
  • d = 17
  • 3 + 7 + 17 = 27

That's my thought process too

Nathan Ferguson - 4 years, 6 months ago

I did the same thing. Except I got an expression for y, the dog, [20-z] where z is the cat and plugged it into the cat and dog expression, x+y=24. Substitution method, it becomes x+(20-z)=24, which simplifies to x-z=4, which lends itself to the combination method since x+z=10

Qahir Mujaimin - 4 years, 5 months ago
Sharad Joshi
Apr 1, 2016

Add all the three total is 54. U have counted all the animals twice so half is 27 & that is d answer.

I do the same thing. Excellent

juliet nawatha - 4 years, 11 months ago
Hadia Qadir
Aug 30, 2015

If you plus the Dog and rabbit(20kg) + the dog and the cat (24kg) = adds to 44kg now u know that cat and rabbit weights 10kg together. Minus that 10 kg from 44kg gives u 34kg 2 dogs left. Now u want to find only one of the dog means u ÷ it by 2 = 17kg one dog

So u can work out that the: Rabbit weights 3kg Cat weights 7kg Dog 17kg

Add all of them total is 27kg

Add all of them total is 27kg

khanueng ngamsrisawat - 1 year, 3 months ago

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If you plus the Dog and rabbit(20kg) + the dog

khanueng ngamsrisawat - 1 year, 3 months ago
Faria Qureshi
Jul 22, 2015

add the weights of the two two animals (cat+rabbit=10) (dog+rabbit=20) so that total weight of a cat, a dog n 2 rabbits become 30 ( 10+20=30) as the third picture says the weight of a cat+dog= 24 so we deduct 24 from 30 (30-24=6) thus 6 will be the weight of TWO RABBITS as these rabbits are identical they must have the same weight so when we divide 6 between 2 it is 3 of each. now for the fourth picture we know that the weight of the cat n dog is 24 n if we add 3 (the weight of rabbit ) it becomes 27. that's it.

Mohammad Khaza
Jul 20, 2017

suppose, Cat =C

Dog=D

and Mouse=M

now, C +M =10 .............(1)

and, D + M=20...................(2)

subtracting (1) from (2) we get, D-C =10................(3)

again, D+C =24..................(4)

from ,(3)+(4), we get, 2D =34, or, D =17

co, C= 24 -17 =7 and M =10-7=3

now, M+D+C =3+17+7=27kg

Ajla Cehajic
Mar 27, 2016

Cat add Bunny is 10. Cat is 7.
Bunny is 3.

7 add 3 is 10.

bunny add dog is 20. If bunny is 3,add on 17 for the dog.

3 add 17 is 20.

Dog add cat is 24 because 17 add 7 is 24.

All them together is 27. All you need to do is add the 3 for the bunny onto the cat and dog. 24 add 3 is 27.😊

Sarah Zuo
Nov 8, 2020

My solution is to try to find the rabbit's weight, and then add it to the cat and dog's weight. If we add the first row of animals' weight, the sum is 30, and the third one is 24kg. As you can see, the two on top has two more rabbits than the third one, which has no rabbits. 30-24=6, so the two rabbits are 6kg. now we divide 6 by two because there are two rabbits and the answer is three. We add the rabbit's weight to the cat and dogs', and we get 27.

Sam Fang
Nov 5, 2020

dog + cat= 24, dog+ rabbit= 20, so cat is 4 kg heavier than rabbit. cat+rabbit= 10 kg, so cat= 7, dog= 17, rabbit=3, so the solution is 27

Fedele Wu
Nov 4, 2020
  • Cat + Rabbit = 10KG ⇥ ①
  • Dog + Rabbit = 20KG ⇥ ②
  • ②-① = Cat + Rabbit -Dog - Rabbit = Cat - Dog = 10 ⇥ ③
  • Cat + Dog = 24 ⇥ ④
  • ③-④ = Cat + Cat + Dog - Dog = 2Cat = 14
  • Cat = 7
  • Dog = 24 - 7 = 17
  • Rabbit = 20 - 17 = 3

Suppose the weight of the cat is x x (kg), the weight of the rabbit is y y (kg) and the weight of the dog is z z (kg).

From the given figure, we have:

( x + y ) + ( y + z ) + ( x + z ) = 10 + 20 + 24 (x + y) + (y + z) + (x + z) = 10 + 20 + 24

\Rightarrow 2 x + 2 y + 2 z = 54 2x + 2y + 2z = 54

\Rightarrow 2 ( x + y + z ) = 54 2(x + y + z) = 54

\Rightarrow x + y + z = 54 2 x + y + z = \frac {54}{2}

\Rightarrow x + y + z = 27 x + y + z = 27

So the total weight of all the three animals is 27 k g \color{#69047E}\boxed{27 kg}

Daniel Tadeja
Oct 9, 2019

(10+20+24)/2

Gia Hoàng Phạm
Sep 20, 2018

Picture Picture

Let a a is a dog, b b is a rabbit & c c a cat

a + b = 10 , b + c = 20 , a + c = 24 a + b + b + c + c + a = 10 + 20 + 24 = 2 ( a + b + c ) = 54 a + b + c = 27 a+b=10,b+c=20,a+c=24 \implies a+b+b+c+c+a=10+20+24=2(a+b+c)=54 \implies a+b+c=\boxed{\large{27}} (kg)s

f ( x ) + d + c + r = 27. 😄😁😀😃😄☺😊😆😇😛😜😝😋 and 😒😦😧😵😎😌😳😐😑😕😴😠😡😬😶😟😔😏

Am Kemplin - 1 month, 2 weeks ago
Bharathi Reddu
Oct 1, 2017

We can add the weights of the first three scales . so 2 dogs + 2 cats + 2 bunnies will have have a weight of 54 . So 1 dog + 1 cat + 1 bunny will be 27

well done . thanks for the easy solution

Bharathi Reddu - 3 years, 8 months ago
Matthew Copping
Jun 27, 2017

A simple way to solve these problems is to simply add together the three total weights and then divide by 2.

Philip Scott
Jul 20, 2016

An important thing to note: the kilogram is a unit of mass, not weight.

You already know that the mass of the cat and the dog is 24kg, so all you really need to figure out is the mass of the rabbit.

Let C C , D D , and R R be the masses of the cat, the dog, and the rabbit, respectively.

According to the diagram,

C + R = 10 C + R = 10

D + R = 20 D + R = 20

Therefore, C + D + 2 R = 30 C + D + 2R = 30

Given C + D = 24 C + D = 24 from the third part of the figure,

C + D + 2 R = 30 C + D + 2R = 30

24 + 2 R = 30 \Rightarrow 24 + 2R = 30

2 R = 6 \Rightarrow 2R = 6

R = 3 \Rightarrow R = 3

Adding R R to C + D C + D will yield 27kg, the sum of the animals' masses.

Geneveve Tudence
May 30, 2016

let r be the weight of rabbit, d be the weight of dog, and c be the weight of cat.

the given equations show:

c+r=10

d+r=20

d+c= 24

Note that:

d=20-r

d=24-c

Meaning,

20-r=24-c

Also note that c+r=10 which gives us c=10-r

So, by substitution,

20-r=24-c

20-r=24-(10-r)

20-r=24-10+r

20-14=2r

6=2r

r = 3 r=3

d=20-3= 17 17

c=10-3= 7 7

So, r+d+c=3+17+7= 27

A G
Mar 28, 2016

C+r=10.  C= r+4 R+4+r=10 2r+4=10 2r=6 R=3 C=3+4=7 D=17

Jenny Braha
Mar 27, 2016

R+C = 10 R+D =20 C+D=24

So if we : C+R+C+D = 10+24 2C+R+D = 34

We add minus both parts -R + (-D) = 20 So: 2C+R+D-R-D= 34-20 2C=14 2C/2 = 14/2 C =7 So:R+7 =10 R= 3 D=17 C+R+D= 7+3+17 = 27

Kashif Ahmed
Mar 25, 2016

x+y=10, x+z=20, y+z=24,

y=10-x, z=20-x,

10-x + 20-x = 24, -2x + 30 - 24 =0, -2x + 6=0, -2x=-6, x=3, y=7, z=17, so x + y + z = 27

Hii Cristine XD
Sep 8, 2015

Solving simultaneously by letting Rabbit = r, Dog = d and Cat = c

c + r = 10 (i)

d + r = 20 (ii)

d + c = 24 (iii)

Now from equ. (i) and (ii) solving for r gives : 10 - c = 20 - d

☞ d - c = 10 solving this with equ.(iii) simultaneously results Cat = 7 kg, Rabbit = 3 kg and Dog = 17 kg

total weight = r + d + c = 27 kg

Surya Santoso
Jul 26, 2015

dog+rabbit= 20 dog+cat=24 (dog+cat)-(dog+rabbit)=4 So, Cat-Rabbit= 4.. Cat+Rabbit= 10, so 7+3 then dog is 17, rabbit 3, cat 7

Pranav Arora
Jul 25, 2015

x+y=10 y+z=20 x+z=24 Solving x,y,z we get x=7 y=3 z=17 x+y+z= 27

Sahba Hasan
Jul 23, 2015

Let,

Weight of Rabbit = R R

Weight of Cat = C C

Weight of Dog = D D

Given,

C + R C+R = 10 = 10 . . . . . . ( i ) ......(i)

D + R D+R = 20 = 20 . . . . . . ( i i ) ......(ii)

D + C D+C = 24 = 24 . . . . . . ( i i i ) ......(iii)

Adding all equations we get,

2 ( C + D + R ) = 54 2(C+D+R) = 54

C + D + R = 54 2 C+D+R = \frac{54}{2}

C + D + R = 27 C+D+R = 27 = A n s w e r Answer

Let the cat be represented by c, the dog by d and the rabbit by r R+C=10 - eqn 1 D+R=20 - eqn2 D+C=24 - eqn3 Add eqn 2 and 3 together 2D +R+C= 44 But R+C = 10 2D+10=44 Collect like terms 2D= 34 D=17 In eqn 2 17+R=20 R=3 but R+C=10, sub R C=10-3=7 Therefore the sum of their weight, D+C+R=17+7+3=27

michael oguamah - 4 years, 8 months ago

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