If a substance has a half life of 45 days, how much of the original substance would be left after 90 days?

Which function is performed by earths atmosphere? a. ultraviolet rays are prevented from reaching the ozone layer. b. earths temperature is raised and moderated by trapping in heat c. charged particles from the sun are prevented from reaching earth. d. magnetic charges from space are prevented from reaching earths surface.

The wave shown on the electromagnetic spectrum disturb the medium it passes through a)different frequency. b)the same frequency .

When you mate two plants together the terms is called? answer it fast as possible plz! i have a test tomorrow!