What is the best way to approach problems like the following?. It would be helpful to get a general idea of the different techniques that gmatters generally use
My basic principle is to use logic rather than formulae... when you read a problem and remember a formula, you try to fit the problem to the formula rather than thinking intuitively.
This will go a long way in solving any problem from combinations to probability. Some might be a bit more involved than others, but usually you can solve them.
There are 5 married couples and a group of three is to be formed out of them; how many arrangements are there if a husband and wife may not be in the same group?
Total of 10 people:
# of ways of picking 1st = 10
# of ways of picking 2nd = 8 (excluding the 1st one's spouse)
# of ways of picking 3rd = 6 (excluding 1st and 2nd's spouse)
Total ways = 10x8x6= 480
How many different signals can be transmitted by hoisting 3 red, 4 yellow and 2 blue flags on a pole, assuming that in transmitting a signal all nine flags are to be used?
Total flags = 3+4+2 = 9
Number of ways of arranging the flags = 9!
As there are 3 red, 4 yellow and 2 blue flags, the arrangement within those colors is replicated.
Therefore total number of signals = 9!/3!2!4! = 1260
Hope I did these correctly, after dishing out "advice" on how to solve these...