Every day, Navya's teacher randomly picks a number from 1 to 80 to be the number of the day. The number of the day can be repeated. There are 180 days in the school year. Predict how many days the number of the day will be greater than 20.

Question

Mathematics

Summer Briggs

Yesterday, 19:47

Every day, Navya's teacher randomly picks a number from 1 to 80 to be the number of the day. The number of the day can be repeated. There are 180 days in the school year. Predict how many days the number of the day will be greater than 20.

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Answers (2)

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Yusuf Bean · Answer 1

Out of all the numbers from 1 to 80, there are (80-20) / (80) = 60/80 = 0.75

of them that are greater than 20.

So every time you pick one at random, there a 75% chance that it will be

greater than 20.

If everything works out according to pefectly random probabilities, then

in 180 selections, 75% of them = (0.75 x 180) = 135 of the selections

would be numbers greater than 20.

Fun Dip · Answer 2

If she uses each number evenly it would be repeated 2.25 times. A number between 20 and 80 would be repeated 3 times. I'm not completely sure though ... but I do believe that it would be 60 days ...