If I have 100 radioactive atoms, and 3 half lives have passed. How many radioactive atoms remain? Explain your reasoning.

Sandstones that form in aeolian (wind/desert) environments appear very different from other sandstones, such as those formed in a beach/ shoreline environment and in rivers on land. give three identifying properties for each of the three sandstones that would tell a geologist which depositional environment they formed in. consider things such as the relationship between transportation and grain size, shape, roundness, sorting, fossils and composition.

What's erosion? a. the breakdown of rock into smaller pieces b. the removal of weathered products from rock c. a change in rock resulting from exposure to water d. a chemical change in rock that weakens it

Which of the following best describes brazil's economy from 1650-1880? a. it gradually shifted to manufacturing as the industrial revolution progressed. b. it was based on mining. c. it was based on plantation agriculture, where slaves served as a labor force. d. it was based on small, family-owned farms.