physics
posted by Mariah .
Assuming biological substances are 90% water and the density of water is 100 kg/meter cubed, estimate the mass of a fly, which can be approximated by a cylinder 4 mm long and 2 mm in diameter (volume (length*pi*radius squared)

Multiply the volume of that cylinder by the density of water.
Your density is ten times too low. You'd better check it again. 
yes I meant the density was 1000 kg/meter cubed. but when I multiply the volume of the cylinder (12.56) by the density of water, (1000), i get 12560. the answer is supposed to be 1.131 X10 to the negative 5th power