maths

[slush]

Can anyone help with this maths question please. It takes 2 dogs 18 days to eat some tinned dog food, how long would it take 3 dogs to eat the same amount of food?
My ds has worked it out but I'm still puzzled. The answer is 12.

Please breakdown working out for me. I have tried doing it using equation method but not much luck.

[mclm]

Hi slush,

Here's how I would explain it:

2 dogs * 18 days = 36 'portions'

36 portions would therefore be eaten by 3 dogs as follows:

36/3 = 12 days

Hope this helps.

[CraftyMinx]

That's what I had too

If 2 dogs take 18 days it would take one dog 36 days to eat the same amount of food. Therefore 3 dogs would take a third of this time, 12 .

2 dogs x 18days = 36 eating days
36 eating days / 3 dogs = 12 days per dog