calculations

marliani.majid:

the weight of the cat and mouse is 10kg, the weight of the dog and mouse is 20kg, the weight of the cat and dog is 24kg, what is the weight of the cat, dog and mouse?

Hi Marliani,

First you write the equations.
C+M=10 (1)
D+M=20 (2)
C+D=24 (3)

now make M the subject of equations1 and 2
Since you have M= as the Left Hand Side of t both of them, you can put the two right hand sides as equal to one another.
Now you can make D (or c) the subject of the new equation.

Now solve the new equation and equation 3 simultaneously to get the values of C and D
then sub back into one of the original equations to get the value of M.

See if you can do it now. Tell you what answer you get or tell me where you get stuck.
Melody.

Its 37kg

27kg )

Hello Varshni and Maya,

Obviously only one of you can be correct.
If you still have the ages for the cat, the dog and the mouse (or if you do it again)

I want you to test the ages out on the original question to check if your answer is correct.
Maybe one of you has already done this.
Anyway I would like you both to tell me and the others on the forum, if your answer is the correct or the incorrect one (and why).

Note: If your answer was wrong and you show us why it couldn't be right then your new answer will be correct. Does that make sense?

Melody.

C+M = 10 , M= 10-C
D+M = 20 , D + (10-C) = 20, D-C = 20-10 =10 , D=10 + C
C+D = 24 , C+ (10+C) = 24 , 2C + 10 = 24 , 2C = 24-10 , 2C= 14 , C= 14/2, C = 7 Cat is 7 kg.
M= 10-C = 10-7 = 3 Mouse is 3 kg
D = 10 + C = 10 +7 = 17 Dog is 17 kg

That's excellent work Jun de Lira, but I still want you to show us how you checked that your answer was correct.