The cascade tunnel in Washington state is the longest railroad tunnel in the United States. It is about 1 4th the length of the Seikan. Seikan is 33.46. About how long is the cascade tunnel?
Well, if something is about 1/4 the length of another thing with a known length, a good start is to multiply the known length by 1/4.
33.46 * [about] 1/4 = [about] 8.365
