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+--- Thread: Riddles, brain puzzles and mathematical problems (/thread-19232.html)
RE: Riddles, brain puzzles and mathematical problems - Bridge - 11-18-2012
It doesn't make any sense to subtract it though, because it's another possibility. In other words, there are three ways in which a current can pass through the circuit:
1) Via the top half (two switches)
2) Via the bottom half (three switches)
3) Via both (five switches)
Why is the solution not (2/3)^3+(2/3)^2+(2/3)^5? I honestly want to know, I have to take a final on this stuff next month and I find probability so vague and indirect.
RE: Riddles, brain puzzles and mathematical problems - BAndrew - 11-18-2012
(11-18-2012, 12:39 PM)Bridge Wrote: It doesn't make any sense to subtract it though, because it's another possibility. In other words, there are three ways in which a current can pass through the circuit:As I said I haven't been taught about possibilities yet at school so I am not exactly sure, but I think
1) Via the top half (two switches)
2) Via the bottom half (three switches)
3) Via both (five switches)
Why is the solution not (2/3)^3+(2/3)^2+(2/3)^5? I honestly want to know, I have to take a final on this stuff next month and I find probability so vague and indirect.
P(A U B) = P(A) + P(B) - P(A+B) *
*P(A+B) is symbolized with an inverted U
RE: Riddles, brain puzzles and mathematical problems - Oscar House - 11-18-2012
(11-18-2012, 12:39 PM)Bridge Wrote: It doesn't make any sense to subtract it though, because it's another possibility. In other words, there are three ways in which a current can pass through the circuit:I think it has less to do with probability and more to do with the way electricity works. The current loops back to where it's coming from, causing a short circuit.
1) Via the top half (two switches)
2) Via the bottom half (three switches)
3) Via both (five switches)
Why is the solution not (2/3)^3+(2/3)^2+(2/3)^5? I honestly want to know, I have to take a final on this stuff next month and I find probability so vague and indirect.
RE: Riddles, brain puzzles and mathematical problems - Bridge - 11-18-2012
(11-18-2012, 01:54 PM)Oscar House Wrote:EDIT: Never mind, what BAndrew posted makes sense (P(AuB) = P(A) + P(B) - P(AnB)).(11-18-2012, 12:39 PM)Bridge Wrote: It doesn't make any sense to subtract it though, because it's another possibility. In other words, there are three ways in which a current can pass through the circuit:I think it has less to do with probability and more to do with the way electricity works. The current loops back to where it's coming from, causing a short circuit.
1) Via the top half (two switches)
2) Via the bottom half (three switches)
3) Via both (five switches)
Why is the solution not (2/3)^3+(2/3)^2+(2/3)^5? I honestly want to know, I have to take a final on this stuff next month and I find probability so vague and indirect.
RE: Riddles, brain puzzles and mathematical problems - BAndrew - 11-18-2012
Is the riddle solved or not? I am confused.
RE: Riddles, brain puzzles and mathematical problems - Bridge - 11-18-2012
(11-18-2012, 03:01 PM)BAndrew Wrote: Is the riddle solved or not? I am confused.Yes, Chronofox said you were correct.
RE: Riddles, brain puzzles and mathematical problems - BAndrew - 11-18-2012
Riddle 3
Create an arithmetic representation that consists of exactly 6 eights (8), has no other numbers and the result is 1000.
The only symbols that may be used are those of addition, subtraction, multiplication, division, square root and brackets. You may also use expontation
In other words use
At least 6 eights -> 8 8 8 8 8 8
and with +,-,*,/,^,√,() try to make it equal to 1000.
It would be nice if someone could write this better so it is more understandable.
RE: Riddles, brain puzzles and mathematical problems - Bridge - 11-18-2012
(8^3+8^3-8-8-8)*8^0
Is this legal?
RE: Riddles, brain puzzles and mathematical problems - BAndrew - 11-18-2012
(11-18-2012, 05:28 PM)Bridge Wrote: (8^3+8^3-8-8-8)*8^0No, you used the digit 0 and the digit 3. Use only eights.
Is this legal?
8^8 for example is legal. 8^2 is not.
RE: Riddles, brain puzzles and mathematical problems - Bridge - 11-18-2012
(11-18-2012, 05:30 PM)BAndrew Wrote:Alright. You did say we were allowed to use exponents though.(11-18-2012, 05:28 PM)Bridge Wrote: (8^3+8^3-8-8-8)*8^0No, you used the digit 0 and the digit 3. Use only eights.
Is this legal?
8^8 for example is legal. 8^2 is not.