For statement two,
"It will take 6 minutes to type the first half of the letter at an average speed of 40 words per minute"
In the back of the book you wrote the equation w/2 = 40(6)
How do we know that half of the letter is exactly half of the words? Common sense tells me when someone is typing they don't stop exactly at the end of a word. Usually they stop at the end of a sentence or at the end of a paragraph. If there were 4 paragraphs in the letter, half of the letter should be the end of the second paragraph. How do we know word is the delimiter, and not letters, sentences or paragraphs?