Sheri's brother gave Sam his collection of stamps when she left for college. At that time, the value of the collection was $420. Eight years later, the stamp collection
was worth $980. What is the rate of change?

In which of the situations can information about tyler be represented by the expression r+3 when r represents information about ray? check all that apply.

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?

Hi my sisters and brothers can tell me the answer because i don’t understand the question