The half life of a substance is 30 days. If there are 4.5 grams to start with, how much will be left after 23 days? Round to the nearest tenth of a gram. Be sure to label your answer.

Which statement describes the term economics? a. it is the study of using limited resources to fulfill wants and needs. b. it is the study of how governments fulfill the wants and needs of nations. c. it is the study of how people spend their money to fulfill wants and needs.

Find the product of (4x + 3y)(4x − 3y). 16x2 − 24xy + 9y2 16x2 − 9y2 16x2 + 24xy + 9y2 16x2 + 9y2

3-12. write each answer with a reasonable number of figures. find the absolute uncertainty and percent relative uncertainty for each answer. (a) [12.41 (±0.09) + 4.16 (±0.01)] x 7.068 2 (±0.000 4) =? (b) [3.26 (±0.10) x 8.47 (±0.05)] - 0.18 (±0.06) =? (c) 6.843 (±0.008) x 104 + [2.09 (±0.04)- 1.63 (±0.01)] =?