A highschool gym teacher randomly selects a group of two players from three students to demonstrate a basketball drill during class the three students consists of two girls andrea and marta and one boy davi.
The sample space of possible groups is listed below.

Let A be the event that both students the coach chooses are girls and B be the event that the first player is a boy.

What is P(A or B), the probability that the coach chooses all girls or boys first ?

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?