maths question

11 Plus Maths – Preparation and Information

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slush
Posts: 18
Joined: Wed Jan 11, 2012 9:36 pm

maths question

Post by slush »

Hi can someone help with this maths question.
2 dogs take 18 days to eat some dog food. how long will it take 3 dogs to eat the same amount of food.

thank you
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: maths question

Post by Guest55 »

2 dogs take 18 days to eat some dog food. how long will it take 3 dogs to eat the same amount of food.
How long would the food last for one dog?

It would last 2 x 18 ie 36 days


So if there were 3 dogs ..36 divided by 3 = 12
Okanagan
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Location: Warwickshire

Re: maths question

Post by Okanagan »

or put another way ⅔ of 18

the number of dogs is 1½ times what it was before -
so 18 / 1½ (or 3/2)
invert the fraction and change divide to multiply to get
18 x ⅔
Guest55
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Joined: Mon Feb 12, 2007 2:21 pm

Re: maths question

Post by Guest55 »

That's not a very clear method imho - inverse proportion needs explanation.
Elizabeth
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Re: maths question

Post by Elizabeth »

If it takes 2 dogs 18 days, then on his own, it would take one dog 36 days.

Therefore, 3 dogs would divide the food equally 36 / 3 = 12.

It would take 12 days, as the other two have said.
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