Question

The 10 letters in "statistics' are each written on equal-sized disks and placed in a bag. A disk is randomly drawn and the letter is noted. Compute the following probabilities:

a. P( i or t) answer from book 5/10

b. P( a vowel or letter s) answer from book 6/10

c. P( a letter in "algrebra" or " geometry") answer from book 4/10

d. P(a letter in "probability" or "certainty") answer from book 7/10

Please show me how the book got those answers.

Answer 1

a) total number of letters =10

total number of i =2

total number of t =3

hence total number of i or t =2+3 =5

P( i or t) =favourable outcome/total outcome=5/10

b)

number of vowels =number of i's +number of a's =2+1=3

number of s =3

hence  P( a vowel or letter s) =(3+3)/10=6/10

c) common letters between "statistics' and "algrebra" or " geometry" are a and t

total number of a=1

total number of t =3

hence P( a letter in "algrebra" or " geometry") =(1+3)/10=4/10

d) common letters between "statistics' and   "probability" or "certainty" are a ; i ;c and t

total number of a=1

total number of t =3

total number of c=1

total number of i =2

hence P(a letter in "probability" or "certainty") =(1+3+1+2)/10=7/10