List the multiples of each award:
24: 1 , 2, 3, 4, 6, 8, 12, 24
18: 1, 2, 3, 6, 9, 18
The greatest common multiple is 6
The greatest number of shelves will be 6.
The formula for half-life is:

A is the amount remaining, P is the initial amount, t is the time that has passed, and h is the half-life of the substance. Plug in the values that you know and solve:

Rounded to the nearest whole number, the density of the substance was about 13<span>mg / cm².</span>