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?

Answer 1

I believe you have made a typo. Surely it is further than 998 km from earth to Jupiter.

Answer 2

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