Please Help!
Remember that in Cynthia's physics class, she must turn in four lab reports. For each report, she earns extra credit if her percent error is less than 5%.
For her second lab report, she calculated the height of a building four times. She got the following four heights.

6.8 m
7.5 m
8.1 m
7.8 m
The true height of the building is 7 m.

What was Cynthia's percent error?

Remember: Take the average of the three measurements before calculating the percent error.

about 6%
about 8%
about 5%
about 7%

there is only one way to arrange all the eight relative to each other because they are not distinct. we have

now there are nine places to place an (and not more than one in one place).   because we have four symbols, we need to choose four of these nine places to insert an . order does not matter because the are not distinct.

thus there are 1 · c(9,4) ways, or, if we calculate it,

thus there are 126 ways to form such "words."

show us the triangle so we can answer it

there were only 2 presidents that were under the age of 45. theodore roosevelt, and jfk, that makes 5%