Given the following of a school with only grade 9 and 10 Completed no community service hours
Completed at least 1 community service hour
Totals
Grade 9’s
50
125
175
Grade 10’s
20
200
220
Totals
70
325
395

Determine the probability that a student has completed at least one community service hour

Determine the odds that a randomly selected student is in grade 9

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?

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

Could somebody me with this radical simplification?