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PROBABILITY (Chapter 10) 223 EXERCISE 10B 1 Jose surveyed the length of TV commercials in seconds. Estimate, to 3 decimal places, the probability that a randomly chosen TV commercial will last: a 20 to 39 seconds b more than a minute c between 20 and 59 seconds inclusive. Length Frequency 0 - 19 20 - 39 40 - 59 60+ 17 38 19 4 2 Paula keeps records of the number of phone calls she receives over a period of consecutive days. number of days a For how many days did the survey last? 10 b How many calls did Paula receive over this 8 period? 6 c Estimate Paulaâs chance of receiving: 4 i no phone calls on a particular day 2 ii 5 or more phone calls on a particular day 0 1 2 3 4 5 6 7 8 iii less than 3 phone calls on a particular day. number of calls per day 3 Pat does a lot of travelling in her car. She keeps records of how often she fills her car with petrol. The table alongside shows the frequencies of the number of days between refills. Estimate the likelihood that: a there is a four day gap between refills b there is at least a four day gap between refills. cyan magenta yellow Y:\HAESE\IB_MYP4\IB_MYP4_10\223IB_MYP4_10.CDR Friday, 7 March 2008 4:21:34 PM PETERDELL 95 Frequency 1 2 3 4 5 6 37 81 48 17 6 1 Age distribution of prison inmates 100 50 75 25 0 5 95 100 50 75 25 0 5 95 100 50 75 25 0 5 95 100 50 75 25 0 5 4 The table alongside gives the age distribution of prison inmates as of December 31, 2007. A prisoner was released on January 1, 2008. Find the probability that: a the prisoner was male b the prisoner was aged between 17 and 19 c the prisoner was 19 or under given that the prisoner was female d the prisoner was 19 or under given that the prisoner was male e the prisoner was female given that the prisoner was aged 60+. Days between refills black Age Female Male Total 15 16 17 - 19 20 - 24 25 - 29 30 - 34 35 - 39 40 - 49 50 - 59 60+ Total 0 5 26 41 36 32 31 24 16 5 216 6 23 422 1124 1001 751 520 593 234 148 4822 6 28 448 1165 1037 783 551 617 250 153 5038 IB MYP_4