The Student Room Group

can you explain this to me :(

Marie has 25 cards. Each card has a different symbol on it. Marie gives one card to Shelley and one card to Pauline. In how many different ways can Marie do this?
there are 25 different choices for the card to give to Marie
now that shes given one away, there are 24 different choices for the card to give Pauline
total ways 25*24
Reply 2
Pretty sure this can be found using factorials.
25!
¬¬¬¬¬
2!*23!
there are 25 possible cards to choose from, each time you take 2 out your left with 23, this gives you and answer of 300 combinations
Reply 3
Original post by adsuudixfra
there are 25 different choices for the card to give to Marie
now that shes given one away, there are 24 different choices for the card to give Pauline
total ways 25*24


that's great tysm. and sorry just to check, if there was a third person, would it be 25 x 24 x 23?
Reply 4
i think its either that or 24*23 either one- I'm actually curious to know so let say if someone else replies
Original post by razzy02
that's great tysm. and sorry just to check, if there was a third person, would it be 25 x 24 x 23?
Reply 5
Original post by sabnas
i think its either that or 24*23 either one- I'm actually curious to know so let say if someone else replies


lool yeah i see how it could be that! it's just the thought process behind it that i find hardest! :/
Reply 6
Original post by razzy02
lool yeah i see how it could be that! it's just the thought process behind it that i find hardest! :/


i get what you mean- paper 2 next week and i cant wait to never have to do maths again in my life!!!!!!!!!11
Original post by sabnas
i think its either that or 24*23 either one- I'm actually curious to know so let say if someone else replies


I would believe its 25*24*23 if it's based on possibilities from the start but that's because I don't understand the logic of just doing 24*23, could you please explain?
Reply 8
Its just as simple as multiplying the number of choices of card each person has e.g for the two people above its the initial number of cards (n) multiplied by the initial number of cards minus 1 (n-1) so n*(n-1).

For adding more people you just continue using this logic so 4 people for example would be n*(n-1)*(n-2)*(n-3).

Its this easy as they are only taking one card each. It would be more complicated if they took more than one card each or there were duplicates or cards etc.
Reply 9
Original post by Wantrepreneur
I would believe its 25*24*23 if it's based on possibilities from the start but that's because I don't understand the logic of just doing 24*23, could you please explain?


Maybe Marie is clumsy and dropped the first card?
Original post by TomW624
Maybe Marie is clumsy and dropped the first card?


Possibly...although I would have hoped they had more of a mathematical reason for thinking of 24*23, I was intrigued to know what it was but as you confirmed, I'm pretty sure it's 25*24*23.
Original post by razzy02
that's great tysm. and sorry just to check, if there was a third person, would it be 25 x 24 x 23?


25*24*23 is correct :smile:

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