1. what is 40% of 30?
2. 120 is what percent of 200?
3. last year there were 260 students in a soccer program. this year, that number increased by 140%. how many more students joined the soccer program this year?
4. josef left a 22% tip on a 120$ dinner bill. how much was in the tip?
5. megan worked 20 hours last week. this week she worked 80% more hours. how many more hours did she work this week?

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

Asmall (but heavy) particle placed in a glass of water will follow a zigzag motion because the particle will bounce off of the water molecules it meets. this is called brownian motion. a physicist simulates this on a computer, by varying the distance a particle can travel (called the mean free length), on average, before it collides with a water molecule and assigning the change in motion to be one of 8 directions, each with a similar probability. by running the simulated particle (with the same mean free length) many times she determines that it should take 15 seconds, on average, for the particle to fall to the bottom, with a standard deviation of 1.5 seconds. next she lets a real particle fall through a glass of water and finds that it took 18 seconds. what does she conclude, and why?

Plz help plz give me the answer