posted by tresha .
space probe Pioneer 11 was lanced April 5, 1973, and reached Jupiter in Dec.1974 traveling a distance of 998 km. How long did it take an electromagnetic signal to travel to earth from pioneer 11 when it was near jupiter?
I believe you have made a typo. Surely it is further than 998 km from earth to Jupiter.
Lets take the worst case using the aphelion distance of 816,500,000 km (I have no idea where 998 km comes from - closest approach of Pioneer 11?)
Speed of light is 299,800,000 m s^-1 or 299,800 km s^-1
so time taken for signal to reach Earth (note capital letter for a planet) is
816,500,000 km / 299,800 km s^-1