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HCF question
Posted: Mon Sep 15, 2014 2:31 pm
by kateJ
My Dad is 54 and my Mum is 36. I can divide both their ages exactly by both my age and my big brother's age. What is the oldest that my brother could be? How old could I be? How old do you think I am?
Answer: Brother = 18 Me: 6
The brother is 18 (HCF of both numbers). But why is the next answer 6 and not 9?
Many thanks
Re: HCF question
Posted: Mon Sep 15, 2014 2:40 pm
by mystery
Was it multiple choice?
Re: HCF question
Posted: Mon Sep 15, 2014 2:44 pm
by parent2013
I'll go with the answer 6 and 9 ( 3 years age gap between brothers seems more reasonable than 12
)
Which book is it from?
Re: HCF question
Posted: Mon Sep 15, 2014 2:52 pm
by kateJ
Thanks parent2013
It's taken from: 'So you really want to learn Maths Book 1' Galore Park. The answer book states that part 2 of the question is 6 or 2 - no mention of 9 at all!
Re: HCF question
Posted: Mon Sep 15, 2014 3:01 pm
by parent2013
Actually on the second thought (after reading the question carefully), it says
"What is the oldest that my brother could be" - which is as you said HCF i.e. 18
Both 6 and 9 seems ok to me.
Gotta go
Re: HCF question
Posted: Mon Sep 15, 2014 3:33 pm
by ToadMum
kateJ wrote:My Dad is 54 and my Mum is 36. I can divide both their ages exactly by both my age and my big brother's age. What is the oldest that my brother could be? How old could I be? How old do you think I am?
Answer: Brother = 18 Me: 6
The brother is 18 (HCF of both numbers). But why is the next answer 6 and not 9?
Many thanks
The answer to 'How old do you think I am?' would surely be 9 rather than 6, if that - how many 6 year olds do you know who are that conversant with their 6 / 9 / 18 times tables ? Unless there is something glaringly obvious that we are all missing, it appears to be a very poorly-written question...
Re: HCF question
Posted: Mon Sep 15, 2014 6:32 pm
by mystery
You said what I was going to say. Galore Park - crazy question and crazy answer. Is the rest of the book like that?
Or maybe there is some significant reason why Mum and Dad would not have produced a baby when they were 45 and 27 respectively or why a 9 year gap should be avoided at all costs?
She had that first child when she was pretty young and her husband was twice her age. Curiouser and curiouser. Do you think he was her teacher?
Do we know who they are? Far more interesting than guessing whether or not it's a genius toddler that wrote the question.
Re: HCF question
Posted: Wed Sep 24, 2014 5:33 pm
by Proud_Dad
Both brother and the questioner could be 18.
The question refers to "big" rather than "older" brother so they could be 2 twins of different weights/heights.
Re: HCF question
Posted: Mon Sep 29, 2014 6:44 am
by mystery