Posted by Lisa on Saturday, January 19, 2008 at 10:59pm.
For MAMMALS, find the munber of:
a) 7-letter words
b) 7-letter word beggining with MA
c) 4-letter words
i) all letters different
ii) 2 letters same,2 different
iii) 2 pairs same letters
iv) 3 letters same
- data management - Damon, Sunday, January 20, 2008 at 1:15pm
I am not doing the problem for you but perhaps I can give you an idea.
Let's see. I have to work with
M M M A A L S
If all letters were different the answer would be 7!, but they are not.
Let me try a simpler example
A A B B
A B A B
A B B A
B A A B
B B A A
B A B A Hmm six of them, not 4!
Looks like permutations of 4 items divided by permutations of 2 As divided by permutations of 2 Bs
4!/(2!*2!) = 4*3*2 /( 2*2) = 6
Let's try it with 3 As and 1 B
A A A B
A A B A
A B A A
B A A A Is that 4!/(3!*1!) ?
4*3*2 /(3*2*1) = 4, sure enough.
Answer This Question
More Related Questions
- Data Management - For PLANETS, find the number of : 4-letter words which must ...
- History - Even though I asked this before, can you please help me with this and ...
- geometry - In the English alphabet, there are 7 capital letters that look the ...
- HSPA Prep - Marybeth is trying to remember her 4-letter password. All she ...
- Maths - A word made by writing the seven letters used to spell "EXAMPLE" in some...
- Math - Substitute numbers for the letters to make the equation true. Same letter...
- Socials Crosswords - Canada and the Twenties... New form of signage? It's 4 ...
- Counting and Probability - How many 2-letter "words" consist of two different ...
- Combinations - Anna was opening a new restaurant, so she went to the sign store ...
- Geometry - Ok i have a crossward puzzle and don't know some of the vocab. Here ...