## #math trivia solution: What are the chances that a class of 20 has 10 girls and 10 boys?

#math trivia: If girls and boys are equally represented in the school population, what are the chances that a class of 20 has 10 of each? — Burt Kaliski Jr. (@modulomathy) October 16, 2012 This is another combinatorics problem. Each seat in the class will be occupied either by a girl or a boy. The … Continue reading »

## #math trivia solution: What are the chances that a given pair of students are born in the same month?

#math trivia: What are the chances that a given pair of students are born in the same month? Assume all 12 months equally likely — Burt Kaliski Jr. (@modulomathy) October 8, 2012 Assuming all 12 months are equally likely, the chances that a given pair of students are born in the same month is 1/12. … Continue reading »

## Keeping the Sky(lab) from Falling

It was a crowd-sourced crisis response of sorts, the anticipated but mostly uncontrollable descent of Skylab from its perch more than 200 miles above the sky back to earth in 1979.  News reports alerted of the impending surrender of the United States’ first space station to the forces of gravity and atmospheric friction, and watchers … Continue reading »

## #math trivia solution: The principal chooses one student from each of 5 classes …

#math trivia: The principal chooses one student from each of 5 classes of 20 for a project team. How many different “rosters” are possible? — Burt Kaliski Jr. (@modulomathy) October 1, 2012 The number of possible rosters is 3.2 million. This assumes that it doesn’t matter in what order the students are chosen for the … Continue reading »

## #math trivia solution: Each day there’s a 20% chance that a given class has a quiz. …

#math trivia: Each day there’s a 20% chance that a given class has a quiz. What’s the chance that at least one of the five classes does? — Burt Kaliski Jr. (@modulomathy) September 25, 2012 To determine the chances that something happens at least once, it’s often easiest to figure out the probability p that … Continue reading »

## #math trivia solution: The five classes eat lunch at separate times …

#math trivia: The five classes eat lunch at separate times. Every day their times are in a different order. How long can this go on? — Burt Kaliski Jr. (@modulomathy) September 17, 2012 There are 5*4*3*2*1 = 120 different possible orders in which the five classes can eat lunch, so this can go on for … Continue reading »

## #math trivia solution: The 20-student class gets the flu …

#math trivia: The 20-student class gets the flu. Every day a different prime number of students is out sick. For how long can this go on? — Burt Kaliski Jr. (@modulomathy) September 10, 2012 There are eight different prime numbers less than or equal to 20 (2, 3, 5, 7, 11, 13, 17 and 19), … Continue reading »

## #math trivia solution: Two friends got in the same class …

#math trivia: The two friends got in the same class. Seats are assigned randomly, 4 rows of 5. What are the chances that they sit together? — Burt Kaliski Jr. (@modulomathy) September 3, 2012 The chances that the two friends are seated next to each other is 8/95.  This can be calculated as follows: The … Continue reading »

## A Universe of Amazing Science and Technology

The most recent and sophisticated of the number space probes sent from Earth to Mars landed on the Red Planet five weeks ago, continuing a remarkable record of exploration of our fascinating neighbor. While most of Earth has been mapped out (at least the parts on land), Mars and the rest of the multi-billion-light-year vast … Continue reading »

## #math trivia solution: 100 students are assigned randomly …

#math trivia: 100 students are assigned randomly to 5 classes of equal size. What are the chances that two friends get in the same class? — Burt Kaliski Jr. (@modulomathy) August 28, 2012 The chances that two friends get in the same class is 19 out of 99. If the classes didn’t have to be … Continue reading »