# Semi difficult question, see if you can do it.Watch

#1
At present time, My father is five times older than me, and I am twice as old as my sister, In two years time the sum of all our ages will be 58,

How old am I?

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10 years ago
#2
8, 40 and 4? 6 + 10 + 42 = 58 :P
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#3
Nice one rav, Kudos to u.
took me longer than that to do it LOL.
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10 years ago
#4
^^agreed.

"you" are 8
sis is 4
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10 years ago
#5
Me = 2x + 2
Sister = x +2
Father = 10x + 2

=

13x + 6 = 58
13x=52
52/13 = 4

So x = 4
You are 2x So you are 8
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10 years ago
#6
ahhh, I misread the 'in two years time' bit
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#7
Ok,

At his next birthday, My dad will be five times older than my Sister was two birthdays ago, Their combined ages NOW are 42,

How old are they both now?
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10 years ago
#8
(Original post by lilangel890)
Me = 2x + 2
Sister = x +2
Father = 10x + 2

=

13x + 6 = 58
13x=52
52/13 = 4

So x = 4
You are 2x So you are 8
Lol I just realised that the boy had to be an even number of years old and can't be that old because his dad is 5 times older than him and they only add up to 58. Doesn't leave many options so you can work it out quick.
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10 years ago
#9
you're 8
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10 years ago
#10
(Original post by U'llGetDuppied)
Ok,

At his next birthday, My dad will be five times older than my Sister was two birthdays ago, Their combined ages NOW are 42,

How old are they both now?
I can't get this one to work, I've been trying for ages!
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10 years ago
#11
(Original post by U'llGetDuppied)
Ok,

At his next birthday, My dad will be five times older than my Sister was two birthdays ago, Their combined ages NOW are 42,

How old are they both now?
Your sister's age now is x, your dad's age is y. At his next birthday (y+1), he'll be five times older than your sister two birthdays ago (5(x-1)), so 5x - y = 6. Their combined ages now are 42, so x + y = 42. Solve simultaneously to get 6x = 48, so x = 8 and y = 34.

The trick is that "two birthdays ago" means "one year ago". I'm 19 (and a bit) now, which means that on my previous birthday I was 19 and on the birthday before that I was 18.
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10 years ago
#12
(Original post by generalebriety)
Your sister's age now is x, your dad's age is y. At his next birthday (y+1), he'll be five times older than your sister two birthdays ago (5(x-1)), so 5x - y = 6. Their combined ages now are 42, so x + y = 42. Solve simultaneously to get 6x = 48, so x = 8 and y = 34.

The trick is that "two birthdays ago" means "one year ago". I'm 19 (and a bit) now, which means that on my previous birthday I was 19 and on the birthday before that I was 18.

^^I'm a idiot - didn't take the whole "2 birthdays ago is only -1 age).

I thought it was weird, having an age of 53/6 years!
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10 years ago
#13
(Original post by gemmalouise)
I can't get this one to work, I've been trying for ages!
You need to do it algebraically - write an expression connecting the two of them and create simultaneous equations.

Spoiler:
Show
Let sister = x and Dad = y
y + 1 = 5(x-2) since in one year, Dad will be five times as old as Sis was two years ago

x + y = 42 since the total of their ages is 42

x=42-y

y + 1 = 5(42-y-2) replace x with (42-y)

y + 1 = 5(40-y)

y + 1 = 200-5y

6y = 199

so y is roughly 33 (33.16666...), which means x is 9

Dad is 33, Sis is 9.

Put the values in to check - I think you get 34 = 35, which is near enough after rounding.

EDIT: Generalebriety beat me to it...
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10 years ago
#14
I did it like this:

me=x
sister=y
father=f

f=5x
x=2y

x + y + f= 58
58-2= 56

x+y+f=56

sub x=2y, f=5x and 5x=10y

2y+y+10y=56
13y=56
y=approx 4

therefore x=8 and f=40.
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10 years ago
#15
I did it pretty much the same as above but slightly differently.

f = father, m = me, s = sister

f = 5m

m = 2s

f + m + s + 6 = 58 ----> f + m + s = 52 ----> 2f + 2m + 2s = 104

10m + 2m + m = 104

m = 8

2s = 8 ----> s = 4

f = 5 x 8 ----> f = 40

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10 years ago
#16
Good old "trial and improvement" got it for me first time round
The second question confused me - the two birthdays ago was what troubled me
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