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yellowhighlighterr

yellowhighlighterr

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ik that the last digit must be 0 or 5, leaving us with the ss now being 8 values.
so p(div by 5) = 8*7*6*1 (if its 0) and the same for 5 (=336+
they both give 336, so wouldn't you just multiply 336 by 2 together to get the answer????
 
synthesisFR

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wait actually my trials r soon and i swear i havent done perms and combs since like prelims 😭 😭
 
yanujw

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yellowhighlighterr said:
heres a weird one
part d
any help pls?
Click to expand...
There are two approaches. First you could think that either N is to the left of U or it isn't, and there is no condition that makes one possibility more likely so there are half as many ways as if there were no restrictions. Thus 6!/2 = 360 ways

Or, visualise just N and U already being there next to each other, and that the other letters are to be placed around them so that N always remains before U. There are 3 positions for the first letter placed, 4 for the next, then 5 and then 6 positions for the final letter placed. Apply the multiplication principle for a total of 360 ways.

synthesisFR said:
just take (NU) as one letter and dont do 2! inside bc thats the only arrangement
then just normal arrangement
Click to expand...
This approach is not quite correct, this places N and U next to each other rather than the premise of the question.
 
yellowhighlighterr

yellowhighlighterr

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yanujw said:
There are two approaches. First you could think that either N is to the left of U or it isn't, and there is no condition that makes one possibility more likely so there are half as many ways as if there were no restrictions. Thus 6!/2 = 360 ways

Or, visualise just N and U already being there next to each other, and that the other letters are to be placed around them so that N always remains before U. There are 3 positions for the first letter placed, 4 for the next, then 5 and then 6 positions for the final letter placed. Apply the multiplication principle for a total of 360 ways.


This approach is not quite correct, this places N and U next to each other rather than the premise of the question.
Click to expand...
could u elaborate further pls?
 
synthesisFR

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yanujw said:
There are two approaches. First you could think that either N is to the left of U or it isn't, and there is no condition that makes one possibility more likely so there are half as many ways as if there were no restrictions. Thus 6!/2 = 360 ways

Or, visualise just N and U already being there next to each other, and that the other letters are to be placed around them so that N always remains before U. There are 3 positions for the first letter placed, 4 for the next, then 5 and then 6 positions for the final letter placed. Apply the multiplication principle for a total of 360 ways.


This approach is not quite correct, this places N and U next to each other rather than the premise of the question.
Click to expand...
OHHHHH that makes sense
yep ignore what i said i was thinking like N and U have to be like right next to each other

this proves my point that i need to relearn this topic before trials 😭
 
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