Kem12 wrote:
I have really tried to understand the concepts applied here from all the explanations but I still don't.Can someone be kind enough to help with a link that explains these concepts clearly...
:-(
Thanks.
Posted from my mobile deviceIf you are struggling with the above methods like me, I'm going to explain to you my way of solving ; However I don't know whether it would be sufficient to clear your doubts or not ?!
There are a TOTAL '7-seats' for the alphabets of the letter 'JUPITER' out of which '3' are vowels & '4' are consonants ;
The question asks us to find the total no. of ways in which vowels will be in a particular order (,i.e, alphabetical order & if it was a no. code maybe the question would have told ascending/descending order) ;
Coming back to the question, we know there are '7-seats' => We have to choose '3-seats' for our vowels ( E, I, & U ) => we can do that in 7C3 ways ;
Or, simply [7!/(3!x4!)] ways [This is what I meant => C C V V V C C, C V C V C V C, C C C V V V C, etc.]
Now, the order of vowels is 'E I U' => Total no. of arrangements = (7C3 x 1)
[And NOT (7C3 x 3!) Since, doing so we would include the arrangements 'UIE, UEI, IUE, IEU, EUI' along with 'EIU' which we don't want as per the question]
Now, we are left with '4-seats' for consonants (J, P,T, & R) => We can choose '4-seats' for '4' consonants in 4C4 (or 1) way ;
[But here we are allowed for arrangements, i.e, JEUITPR, JEUITRP, EUIJPRT, EUITPR, etc] ;
Hence, we can do it in 4C4x4! ways ;
THEREFORE, TOTAL NO. of WAYS IN WHICH VOWELS STAYS IN ALPHABETICAL ORDER IN 'JUPITER' = 7C3x1x4C4x4! = 840 ways = option D.
Hope it helps...