Q4 of 18 Page 69

Number from 1 to 50 are written on slips of paper and put in a box. A slip is to be drawn from it; but before doing so, one must make a guess about the number: either prime number or a multiple of five. Which is the better guess? Why?

Prime numbers between 1 – 50:


2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43 and 47


Multiples of five:


5, 10, 15, 20, 25, 30, 35, 40, 45, 50


Number of prime number from 1 to 50 = 15


Number of multiples of 5 from 1 to 50 = 10


Total number of paper slips = 50


Probability of getting a prime number



⇒


Probability of getting a multiple of 5



⇒


From the calculated probabilities, we can observe that the probability of getting a paper slip which has prime number is 0.30 and the probability of getting a paper slip which has a multiple of 5 is 0.20.


Hence, choosing a prime number would be better because the probability of getting a prime number paper slip is higher than probability of getting a multiple of 5.


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