A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship that travels away from Earth at a speed of 0.60c for 10 years (as
Measured by Courtney). At the end of the trip, Courtney is 20 years old. How old is Andrea?
A) 12 years
B) 10 years
C) 20 years
D) 18 years

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The Answer of A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship that travels away from Earth at a speed of 0.60c for 10 years (as
Measured by Courtney). At the end of the trip, Courtney is 20 years old. How old is Andrea?
A) 12 years
B) 10 years
C) 20 years
D) 18 years

A Set of Twins, Andrea and Courtney, Are Initially 10