Question

Twenty one-slips of paper are each marked with a different letter of the alphabet and placed in a basket. A slip is pulled out, it’s letter recorded and the slip is replaced. This is done 6 times. Find the probability that the word riddle is formed. Assume that each letter in the word is also in the basket

Answer 1

Answer:

4 / 85766121  or 0.00000004664  to  11 decimal places.

or about 5 in 1 hundred million!

Step-by-step explanation:

Probability ( any letter other than d is drawn) = 1/21 as only d occurs more than once in riddle.

Probability (a letter d is drawn) = 2/21  because there are 2 d's in riddle.

To get our answer we multiply probabilities because each drawing of a letter is independent of other draws.

So the Probability of the word drawn being riddle

= 1/21* 1/21*2/21*2/21*1/21*1/21.