probability problem

probability problem

Posers and Puzzles

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T

Joined
19 Oct 03
Moves
69376
13 Mar 05

You and a friend are playing Scrabble, which involves lettered tiles. Here is the distribution of the tiles:

A:9 B:2 C:2 D:4 E:12 F:2 G:3
H:2 I:9 J:1 K:1 L:4 M:2 N:6
O:8 P:2 Q:1 R:6 S:4 T:6 U:4
V:2 W:2 X:1 Y:2 Z:1 Blank:2

At the start of the game, you choose seven letters. Solve the following, showing all work.

a) what is the probability that you will choose three vowels and four consonants? (counting 'Y' as a vowel)

b) what is the probability that you will choose the letters A,B,C,D,E,F, and G in order?

A calculator is going to be needed. Have Fun!

T

Joined
29 Feb 04
Moves
22
14 Mar 05
4 edits

Originally posted by TDR1

a) what is the probability that you will choose three vowels and four consonants? (counting 'Y' as a vowel)

b) what is the probability that you will choose the letters A,B,C,D,E,F, and G in order.


There are
9 A's
12 E's
9 I's
8 O's
4 U's
2 Y's
So total vowels = 44

There are
100 tiles
2 Blanks
So total consonants = 98 - 44 = 54

a) Number of ways of arranging 3 vowels and 4 consonants = 7! / 3! 4! = 35
Number of ways of choosing 3 vowels and 4 consonants in a particular order = (44*43*42)*(54*53*52*51) / (100*98*97*96*95*94*93)
149586723 / 18796757000

Hence probability of choosing 3 vowels and 4 consonants in any order
149586723 / 537050200
= 0.2785339676

b) Required probability = 9*2*2*4*12*2*3 / (100*98*97*96*95*94*93)
= 1 / 723675144500
= 0.00000000000381835493

T

Joined
29 Feb 04
Moves
22
14 Mar 05
2 edits

Originally posted by THUDandBLUNDER
Number of ways of choosing 3 vowels and 4 consonants in a particular order = (44*43*42)*(54*53*52*51) / (100*98*97*96*95*94*93)


Oops, that should be
Number of ways of choosing 3 vowels and 4 consonants in a particular order = (44*43*42)*(54*53*52*51) / (100*99*98*97*96*95*94)
= 4532931 / 606347000

Hence probability of choosing 3 vowels and 4 consonants in any order
= 4532931 / 17324200
= 0.2616531211

G

Cincinnati, USA

Joined
28 Aug 04
Moves
9069
15 Mar 05

But that doesn't account for the possibility of one or two of the seven tiles being blanks, which can be used as either vowels or consonants.

T

Joined
29 Feb 04
Moves
22
15 Mar 05

Originally posted by Gyr
But that doesn't account for the possibility of one or two of the seven tiles being blanks, which can be used as either vowels or consonants.
I believe the question was about how the tiles are chosen, not about how they are played.