A single grain of sand occupies a volume of about 0.004 cubic millimeters. Based on your previous answer,

how many grains of sand are on Earth's beaches?

5 sextillion grains of sand

Explanation:

If the volume of a single grain of sand is 0.004 cubic millimeters, then there will be about 8 x 10^9 grains of sand in a cubic meter. If the volume of all the beaches is roughly 7 x 10^11 cubic meters then there will be 5 sextillion grains of sand on all earth beaches.

2 & 23

Explanation:

Calculate the number of grains in two steps.

First, calculate the volume of one grain of sand in cubic meters:

0.0044 mm3 * =.

Then, calculate the number of grains of sand on the beaches:

7 * 1011 m3 * = 2 * 1023 grains.