istance of a planet from sun is four times the distance of the planet frpm earth.How many years will the planet take to complete one revolution of sun?

Answer 1

recall Kepler's 3rd law:

P^2/a^3 is constant

Now we have to interpret your statement. As it is, it is rather ambiguous. Read it carefully.

Assuming the most convenient meaning, I'll say that if we substitute 4a for a, we have to find P' such that

P'^2/(4a)^3 = P^2/a^3
P' = 8P

so, the period is 8 times as long.