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- Homework Statement
- One twin leaves earth on his 25th birthday traveling at velocity .87c. After traveling away from earth for 5 Earth-years, he abruptly turns anround and travels back to Earth at the same speed. How old will his twin brother be, whom he left on earth? How old will he be?

- Relevant Equations
- Unclear

So at first I thought that the time would be 10 years, and that I’d have to consider the outbound motion as v = .87c and inbound motion as v = -.87c but I’m struggling with addition of the velocities and whether or not this is even the right approach?