Time + probability - practice problems
Number of problems found: 36
- The usage
The battery usage time installed in a particular smartphone has a Normal distribution with a mean of 25.2 hours and a standard deviation of 7.5 hours. What is the probability of usage time greater than 32? - A basket 4
A basket contains 9 fruits, where 4 are oranges, and the rest are mangoes. Three fruits are taken out one at a time and put aside. Find the probability that 3 are oranges. - Ekene and Amina
The probability that Ekene will be alive in 5 years' time is 3/4, and the probability that his wife Amina will be alive in 5 years' time is 2/5. Find the probability that in 5 years' time: a) both of them will be alive b) only Ekene will be alive - Bulb life
Tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. Find the probability that a randomly selected light bulb will last between 675 and 900 hours. - Five roommates
Five roommates will move into a house with four bedrooms: one double room and three single rooms. The five roommates propose that they draw names to determine the order in which they pick the bedrooms, assuming that the first three names drawn will choose - False positive, false negative
Suppose the likelihood of someone being allergic to cats is 1/1000 of the general population. A test to determine if you're allergic to cats has a false positive rate of 5%; that is, 5% of the time, the test will indicate incorrectly that you are allergic - Bernoulli trial
A used car saleswoman estimates that each time she shows a customer a car, there is a probability of 0.1 that the customer will buy the car. The saleswoman would like to sell at least one car per week. If showing a car is a Bernoulli trial with a probabil - Suppose 6
Suppose the life span of a revolutionary light bulb is normally distributed with a mean life span of 70 thousand hours and a standard deviation of 3 thousand hours. If a light bulb is chosen at random: a) what is the probability the life span will be with - Probability 71164
We roll the dice twice. What is the probability that if an even number falls for the first time, the even number will fall a second time? - Probability 66644
Oskar observes the arrivals and departures of cars in the parking lot. At one point, there were 99 cars in the parking lot: 25 red, 17 white, and the rest were black. What is the percentage probability that a black car was leaving the parking lot at a giv - Probability 63434
There are tickets with the numbers 1, 2, 3, 4, 5, 6, 7, and 8 in the envelope. Two tickets are drawn from the envelope at a time. What is the probability that the sum of the numbers drawn will be 7? Write the result as a decimal rounded to hundredths. - Probability 53061
One hundred people work in the office. Each of them spends an average of 25 minutes daily on the phone. A working day has 8 hours. What is the probability that ten workers will be on the phone simultaneously in one day? - The spinner
The spinner below is spun 12 times. It landed on I 4 times, II 7 times, and III 1 time. What is the difference between the experimental and theoretical probabilities of landing on the II? - Twenty
Twenty swallows sit on a 10 m long telephone cable. Assume that swallows are completely randomly distributed along the line. (a) What is the probability that more than three swallows sit on a randomly selected section of cable 1 m long? (b) What is the pr - Statistical survey
Write TRUE OR FALSE for each question: 1 Standard deviation measures central location. 2. The most frequent observation in a data set is known as the mode. 3 The most passive method of data collection is observation. 4 Access time for secondary data is sh - Probability 37381
The machine produces one part in 2 minutes. The probability that it is defective is 0.05. What probability will the machine produce exactly ten defective parts per shift (8 hours)? - Wimbledon finals
Serena Williams made a successful first serve 67% 0f the time in a Wimbledon finals match against her sister Venus. If she continues to serve at the same rate the next time they play and serves six times in the first game, determine the probability that: - Goalkeeper
Mike plays as the goalkeeper 50% of the time if Peter is the coach in a football game. But if Robert is coaching, he only has a 30% chance. Peter coaches more than Robert in about 6 to 10 games. What is the probability that Mike gets to be the goalie toda - Probability 34801
Last year, it rained 12 days in March. What is the probability that it rained on March 20? - Assembly time
The assembly time for the toy follows a normal distribution with a mean of 75 minutes and a standard deviation of 9 minutes. The company closes at 5 pm every day. If one starts assembling at 4 pm, what is the probability that he will finish before the com
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