Tricky maths questions
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Tricky maths questions
I have been tearing my hair out trying to work out this question, which everyone else would probably find easy!
It suddenly struck me that I could ask the good people on this forum who are always swift to come to people's aid.
Rambling over... question:
Ben is 3 years older than his sister and a third of the age oh his mother. His father is 4 years older than his mother and four times the age of his sister. How old is Ben???
arrrrrrhggh!!
It suddenly struck me that I could ask the good people on this forum who are always swift to come to people's aid.
Rambling over... question:
Ben is 3 years older than his sister and a third of the age oh his mother. His father is 4 years older than his mother and four times the age of his sister. How old is Ben???
arrrrrrhggh!!
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- Joined: Sat Jul 24, 2010 10:45 pm
Re: Tricky maths questions
I usually try to draw questions like that - would start with writing down initials and arrows between them to make it easier to see how the relationships work, so e.g. S----->+3----->B for 'Ben is 3 years older than his sister' etc. With this particular one, you could arrange all four people in a shape of a square, with each corner being an initial of a person and arrows showing age relationships between them. All you need to do then is to see who is the person that you can link everyone's age to. I hope this helps.
Last edited by PurpleDuck on Mon Jul 11, 2016 10:44 pm, edited 1 time in total.
It felt like I hit rock bottom; suddenly, there was knocking from beneath... (anon.)
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Re: Tricky maths questions
hi purpleDuck, thanks for replying....PurpleDuck wrote:I usually try to draw questions like that - would start with writing down initials and arrows between them to make it easier to see how the relationships work, so e.g. S----->+3----->B for 'Ben is 3 years older than his sister' etc. With this particular one, you could arrange all four people in a shape of a square, with each corner being an initial of a person and arrows showing age relationships between them.
will try but i' sure i won't get the answer.
Previously, I tried sister's age as "x"
so Ben = 3 + x = 1/3 of mum's age (say "y")
then dad is 4 = y
dad is also 4x (4 times sister)
that's as far i could go without knowing how to substitute!
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Re: Tricky maths questions
OK, try this (you don't need formal algebra/substitution to do it):
S+3=B and Bx3=M and M+4=D
at the same time, we know that Sx4=D
Can you see where I am going with this?
S+3=B and Bx3=M and M+4=D
at the same time, we know that Sx4=D
Can you see where I am going with this?
It felt like I hit rock bottom; suddenly, there was knocking from beneath... (anon.)
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Re: Tricky maths questions
i can,.... but i just can't see what the next step is. i'm so glad this is anon - very embarrassing!!
Re: Tricky maths questions
Try finding a multiple of 4 which is also a multiple of 3 (so could be mum's age), then look to see whether adding another 4 (for dad's age) gives you a number which is four times the number which is three years less than the number which is a third of mum's age. Not explaining this very clearly
Possible age for Ben: 1 ... ... 6
Possible age for mum (B*3): 3 ... ... 18
Possible age for dad (M+4): 7 ... ... 22
Possible age for sis (D/4): (7/4) ... (22/4)
Obviously, the ages one is looking for are a bit higher. Also can't get things to line up very well, but hint, think KS3, KS4 ages.
Possible age for Ben: 1 ... ... 6
Possible age for mum (B*3): 3 ... ... 18
Possible age for dad (M+4): 7 ... ... 22
Possible age for sis (D/4): (7/4) ... (22/4)
Obviously, the ages one is looking for are a bit higher. Also can't get things to line up very well, but hint, think KS3, KS4 ages.
Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx
Re: Tricky maths questions
Algebra is notoriously difficult with age questions.
No need to try 12 or 24 ... too young
Mum 36 so Ben 12 and sister 9 so Dad 36 x does not work
Mum 48 so Ben 16 and sister 13 so Dad 52 which works ... [4 more than Mum]
Try a few ages for Ben's mum as it must be a multiple of 3 and 4 [because of what it says about Dad's age].Ben is 3 years older than his sister and a third of the age of his mother. His father is 4 years older than his mother and four times the age of his sister. How old is Ben???
No need to try 12 or 24 ... too young
Mum 36 so Ben 12 and sister 9 so Dad 36 x does not work
Mum 48 so Ben 16 and sister 13 so Dad 52 which works ... [4 more than Mum]
Re: Tricky maths questions
Ooh, I was trying to be good and not actually post the answerGuest55 wrote:Algebra is notoriously difficult with age questions.
Try a few ages for Ben's mum as it must be a multiple of 3 and 4 [because of what it says about Dad's age].Ben is 3 years older than his sister and a third of the age of his mother. His father is 4 years older than his mother and four times the age of his sister. How old is Ben???
No need to try 12 or 24 ... too young
Mum 36 so Ben 12 and sister 9 so Dad 36 x does not work
Mum 48 so Ben 16 and sister 13 so Dad 52 which works ... [4 more than Mum]
Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx
Re: Tricky maths questions
As the previous hints had not helped I decided to break my rule about answers.
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Re: Tricky maths questions
as this DP was being so thick you had no choice
i feel for the poor kids who have to learn this at the tender age of 10!
thanks so much all.
i am too ashamed to say my answers came out at 7, 21 and 25
i feel for the poor kids who have to learn this at the tender age of 10!
thanks so much all.
i am too ashamed to say my answers came out at 7, 21 and 25