The mass of a potato cylinder is 40g before being left in a solution, and 80g afterwards. What is the percentage change in mass of the cylinder? Very easy, Thanks for whoever answers it, I also don't know how to mark people as the brainliest on a computer so could someone tell me in the comments? thank you

Scientists are conducting a study on the effectiveness of a new drug on memory loss. they are giving some of the test subjects the new drug to find out if it improves their long-term memory. which are possible limitations of this study? check all that apply. a) test subjects may want to participate in additional experiments. b) test subjects may think they should be paid more. c) test subjects may get bored and want to quit early. d) test subjects may have to travel during the experiment. e) test subjects may have full-time jobs. this is multiple choice. you for the !