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.