Scribe Post2

(1) Twelve people, including you, are member of a choir. The choir director is going to choose three members to attend a workshop. The probability you and two other members will be chosen is: d.) 1 c.) 1 a.) 1 b.) 3 10 12 4 10 1 How we get ? 4 probability that two other probability that you are member will be chosen included in the workshop 1 C 1 11 C 2 55 1 = = C 3 220 4 12 probability that 3 members will be choose from 12 members

(2) Rex is playing a guessing game. The probability he will guess each question correct is 0.3.What is the probability he will guess exactly 5 out 10 questions correctly? a.) 0.15 b.) 0.10 c.) 0.29 d.) 0.80 How we get 0.10? R R R R R W W W W W (0.3)(0.3)(0.3)(0.3)(0.3) (0.7)5 probability of getting probability of probability of 5 correct out wrong answers right answers of 10 questions (0.7)5 (0.3)5 C 5 10 0.00243 0.16807 252 0.1029 or 0.10

(3) You choose four digits from the numbers 09 ( ten digits in total ), with no repeated digits. To win a prize, only two of your numbers need to match the four selected by a computer. The probability, correct to the nearest hundredth, that you will win a prize is: choosing 2 numbers from 4 choosing 3 numbers from numbers multiply by 4 numbers multiply by choosing 4 chooosing 2 numbers choosing 1 number from digit number from 6 remaining numbers 6 remaining numbers 4 C 3 6 C 1 4 C 2 6 C 2 4 C 4 + + 10 C 4 10 C 4 10 C 4 probability of choosing 4 digit number from 10 digit number + 0.0048 + 0.1143 0.4286 0.5476 54.76%

(4) The serial number of a $10 bill contains 8 digits. If your $10bill contains the digit 7 at least once, you win a prize. What is the probability that your $10 bill will win? P ( no. 7's) = (0.9)8 P (at least one 7) = 1 (0.9)8 = 0.5695 = 56.95%

(5) John takes a lunch to school on two days, and on the other three days he buys it. If he takes lunch he is late for his period 4 class 15% of the time, but if he buys it he is late 35% of the time. first we can make a tree diagram and then make a sample space: legend: TL Take Lunch L 0.15 P (TL L) = 0.21 B Buy lunch L Late TL N Not late N0.85 2 P ( TL N) = 0.39 5 L 0.35 P ( B L ) = 0.06 B N0.65 3 P ( B N ) = 0.34 5

a.) What is the probability that John arrives on time? we have to add the probability that John take a lunch and not late and the probability that John buy his lunch and not late P ( TL N) + P ( B N) + 0.34 0.39 P ( arrive on time ) = 0.73 = 73%

(b) If John was late, what is the probability that he took his lunch to school? P ( TL L) = P ( TL L) P ( TL L) + P (B L) 0.06 = 0.06 + 0.21 0.06 = 0.27 = 0.2222 = 22.2%

Scribe Post2

by precious_012526 on Jan 15, 2008

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Scribe Post2 — Presentation Transcript