# another problem

By lonely_f16

@lonely_f16 (2147)

Philippines

March 22, 2007 3:30am CST

i'm really sorry but do you know why the answer is like this
How many 5-letter codes end in a vowel from the name naomi? and the answer is 72 may i ask why?

1 response

@vesuvius (1677)

• Philippines

22 Mar 07

This time, I think the answer is correct...
The trick in problems like this is what I would call the 'slot technique'.
In this problem there are 5 'slots'. On the last slot, you place a 3 since there are 3 vowels [that is the condition of the problem]. Then on the first slot put a 4 [since 4 letters are remaining], 3 on the second slot, 2 on the third slot and 1 on the fourth slot. With this, you have:
4x3x2x1x3=72!
I really hope I'm helping you...

1 person likes this

@lonely_f16 (2147)

• Philippines

22 Mar 07

hey thanks I appreciate your response...you're really intelligent..you earn a plus..if it's not too much for you ..can i ask another? In how many ways can 2 physics book, 4 mathematics books and 3 chem books be arranged in any order but must be together? the answer is 1,728 why is it?

1 person likes this

@vesuvius (1677)

• Philippines

22 Mar 07

I think the answer is correct but I guess it's gonna be difficult to explain the answer to this at mylot...
I'll try anyway...
There are 2! ways in rearranging the physics books, 4! ways for math and 3! for chem. Since there are 3 types of books which should be together, there are 3! ways in which these book categories can be rearranged..
Finally: 2!x4!x3!x3! = 1728!
I know it might be a little too vague at this window because explaining this problem might really require an illustration... But I still hope I'm giving you the aid that you need...