Two trains are traveling towards each other. One is traveling at twice the speed of the other. They started traveling at the same time from two separate stations that are 405 miles apart. In three hours the trains pass each other. Find the rate that each train is traveling.

maybe showing the graph would

step-by-step explanation:

-387129 iq

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."