1. The problem statement, all variables and given/known data In the twin paradox suppose the twins are named Dick and Jane. And they both are 20 years old.Dick takes off on a voyage at a speed of 0.8c to a star 20 light years away.Lets say that both the twins send each other signals once a year while Dick is away.How many signals does Jane receive? 2. Relevant equations This problem is from the book "Concepts of Modern Physics" by Arthur Beiser. I have understood the part about how many signals are receive by Dick. And I am utterly at a loss to explain the signals received by Jane. 3. The attempt at a solution Since for Jane the total journey by Dick is 50 years (25 going and 25 returning). And by relativistic calculations each twin receives 1 signal per 3 years while they are being separated and they receive 3 signal per year when Dick is returning. So while Dick is on his way to reach the star Jane should receive (25/3) = 8 signals.But the book mentions that Jane receives ( (25+20)/3 ) = 15 signals while Dick is journeying to the star. I cant understand where this 20 came from.