Math problems with scientific notation.

Im stuck on a couple of questions for maths. Heres the questions.

1. A cyclotron produces high speed particles. A particle moving inside cyclotron takes 9.5 x 10 to the power of negative 10. seconds to travel 2.1 10 to the power of negative 1 meters....

Calculate the speed of the particle in meters per second (m/s)

2. A planet takes 88 days to travel round the sun. The path of the planet is a cycle is a circle with a diameter of 3.4 x 10 to the power of 8 kilometers. Find the speed of the planet as it travels round the sun. Give your answer in km per hour (km/hr), correct to 2 sig figs.

3. The mass of water on the earth's surface is 1.54 x 10 (to the power of 19) tonnes. The total mass of the earth is 5.84 x 10(to the power of 22) tonnes. Express the mass of water as a percentage of the total mass of the earth giving your answer in scientific notation correct to 2 sig figs.

I dont just want you to tell me the answer, that would be kind of cheating and I wouldnt learn anything from it. Could you please tell me how to do this? I asked my teacher and he said I could do the work he said do what you can but I cant do any of this. So any help will be most useful.

thanks.

1. 4.50 m/s
working:
T= 0.00000000095 s
D= 0.02110 m

S= D
-
T

S= 0.02110
---
0.00000000095

S= 4.50 m/s

2. 505492.42 km/h
working: T= 2112 hours
D= 3.14x 340000000
= 1067600000km

S= D
_
T

S= 1067600000
___
2112

S= 505492.42

3. 8.99x 10 (5)%
working:
mass of earth= 58400000000000000000000
mass of water= 15400000000000000000

% mass of water= 584000
___ x154 = 899360
100 = 8.99x 10 (5)%

1. 4.50 m/s
2. 505492.42 km/h
3. 8.99x10 5