As an event becomes less likely to occur what happens to its probability

Weak battery is considered to be a part of routine a. inspection b. wear and tear c. maintenance d. check

Which number produces a rationale number when multiplied by 1/5

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?