where am i going wrong??? mass of a planet?

Question

A planet orbiting a star is occasionally hit by comets. Each comet has a mass of 1.2 × 104 kg of which 40% is rock and 60% is water ice.
Each time a comet hits the planet 20% of the mass of the comet is vaporised and the rest is added to the planet, increasing the mass of the planet.
If 16 comets hit the planet every 100 years, by how much will the mass of the planet have increased in 1 million years?

How much of the additional mass will be in the form of rock, assuming that the rock and ice evaporate in the same proportions as exist in the original comet?

Increase in mass of planet after 1 Ma.....i got 1.5*10^9 but it does not seem to be right....any ideas where i'm going wrong??
Additional mass of rock after 1 Ma......i got 4.5*10^8 and again that's said to be wrong...i'm confused can anyone help??

Answer 1

7 septillion tons

Answer 2

I also get 1.536x10^9kg, I'm not really sure what's wrong about it.



For the second question I get 5.65x10^8kg. I got that from multiplying 1.536x10^9 by .4 (40%) and then multiplying that by .92 (92%). I did that because 20% of 40% is 8%, so that leaves 92% rock that hits the surface.

Answer 3

I think it may be the amount of significant figures you are using



first answer would be 2 x 10^9



next would be 5 x 10^8



good luck