Radium-226 is a radioactive element, and its decay rate is modeled by the equation R = R0e-0.000428t. How many years will it take for 100 grams of radium-226 to reduce to half its mass?
A.
810
B.
1,620
C.
2,690
D.
5,380

There were 25 students who answered to a survey about sports. four-fifths of them like football. how many students like football?

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?

Which of the following would be a correct step in proving that triangle abc is congruent to triangle cda? a. use a protractor to measure the angles and show that all the corresponding angles are equal in measure. this will allow you to prove congruence by aaa. b. show that segment ab is parallel to segment cd and segment ad is parallel to segment cb. this will allow you to prove congruency by asa. c. show that is segment ab is perpendicular to segment ad. this will allow you to prove congruence by sas. d. none of the above.