Need help with math asap [NL]

Basically, i'm stuck with 1 simple one... but I forgot how to do it.

who can help me this early in the morning?

A mother, her daughter and her grandchildren are on a party.
The mother and her daughter are 109 years old together
The mother and her granddauger are 85 years old together
The daughter and the granddaughter are 56 years old together

How old is the mother?

Ook even in het nederlands. Ik kom er niet meer uit. ben het trucje vergeten.

Een moeder, haar dochter en haar kleinkinderen zijn samen op een feestje.
De moeder en haar dochter zijn samen 109 jaar.
De moeder en haar kleindochter zijn samen 85 jaar.
De dochter en de kleindochter zijn samen 56 jaar.

Hoe oud is de moeder?

PLEASE HELP ME :<
Comments
28
if u change in terms of x + y = # it might be easier for u

edit : i got 69.5, could easily have fucked up tho
It's exactly 69.
Parent
you would be correct.
Parent
mother = 69
daughter = 40
granddaughter = 16
most importantly, how did you get to those numbers?
Parent
x + y = 109
x + z = 85
y + z = 56

and then u just isolate some variables :)
Parent
x= mother
y= daughter
z= granddaughter

x + y = 109
x + z = 85
y + z = 56

You should try to get ONLY one variable on one side, e.g. z = 56 - y and insert it in the other equation so there's only one variable left. (x + 56 - y = 85 -> x = 29+y -> 29 + 2y = 109) Just go on like that till you got all those variables isolated and thus you can calculate the exact number.
Parent
wie cool, das du um die uhrzeit noch sowas erklärst ;D
nett...ich hab schon längst abgeschalten und frag mich,wie ein 23jähriger das nicht rausbekommt...

aber du bist hilfsbereit. es gibt doch noch gute menschen ;D
Parent
Hab ihm sogar den That's the exact way if you still can't figure out how to do it:

x + y = 109
x + z = 85
y + z = 56 | -y

z = 56 - y

x + 56 - y = 85 | -56+y
x = 85 - 56 + y
x = 29 + y

x + y = 109
29 + 2y = 109
2y = 80
y = 40

x+40= 109 | -40
x = 69

y+z = 56
40+z = 56| -40
z = 16
pm'd. :DD

Ich hab Schule in zwei Stunden, wenn auch nur 90 Minuten, und schlafen gehen lohnt sich nicht mehr, da muss ich mir die Zeit anders vertreiben.
Parent
gut gemacht :D
Parent
First of all. I'm in luck that I can read a couple words of german.

I forgot how it works. It has nothing to do with age. And you wanna know why I wanted to know this? Cuz I have to be able to explain how it works. and now I do thanks to carlito! And not because of you grumpy yerman!

Peace out
Parent
hey! it wasnt meant to be offensive, i just saw your age and the question...glad you solved your probs.
Parent
maybe because its 10 years ago he had it at school?
Parent
hei my deaaar
Parent
haj carlito! :)
Parent
oh thank you so much for that comment
stop calling me fag, ok?
Parent
what you need it for? i saw you are 23 years old...just curious..no offence
;DDDDDDdddddddddd
Parent
Way to easy...
It's still fresh in your mind kiddo :P
Parent
Van kleinkinderen naar kleindochter? =D
i hate maths, so overrated
just set up a simple equationsystem...
m... age of mother
d... age of doughter
g.... age of granddoughter

m+d=109
m+g=85
d+g=56
--------------

==> g=85-m || d=56-g=56-85+m
use d to solve the first equation:

2m-29=109
m=69
QuoteA mother, her daughter and her grandchildren are on a party.
The mother and her daughter are 109 years old together
The mother and her granddauger are 85 years old together
The daughter and the granddaughter are 56 years old together


Mother+daughter+mother+gdaugher- (daughter+gdaughter) = 109+85-56
2 mothers = 138
Mother = 69
that's how i did it :D
Parent
Those other solutions are technically right, but they just don't look intuitive to me with all those variables and letters and shit... They just look forced
Parent
yup this solution is found by logical thinking not some formula :)
Parent
Back to top