Voyage to A. Centauri

The spacecraft Voyager was launched from Earth 35 years ago (as of 9/5/12) and is at what is considered the outer cusp of our solar system, having travelled 11.3 billion miles. Alpha Centauri, the nearest star to our sun, is 4.37 light-years away. How long would it take Voyager to reach Alpha Centauri at the rate it is traveling? (Assuming it were pointed in that direction.)

Answer:
Over 79 thousand years. (Don't wait up!)

Calculation:
Light travels 186,000 miles/second. There are 60 x 60 x 24 x 365.25 = 31,557,600 seconds in a year. Therefore there are 186,000 x 31,557,600 = 5.87 x 10¹² miles in a light year. That makes Alpha Centauri 4.37 x 5.87 x 10¹² = 2.57 x 10¹³ miles away. That means that Voyager would have to travel 2.57 x 10¹³ / 11,300,000,000 = 2,270 times the distance that it has already travelled. Therefore it would have to travel 2,270 x 35 = 79,765 years to make the trip.