Asailboat travels a distance of 2 1/2 miles in 1/6 of an hour. which complex fraction represents the unit rate in miles per hour?
a: 2/12 / 1/6
b: 5/2 / 1/6
c: 1/6 / 5/2
d: 1/6 / 2 1/2

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?