Melvin wants to buy 9 pencils at a cost of $1.75 each. What is the least number of $2 notes that he needs to buy the pencils?
The total cost of 9 pencils at $1.75 each is 9 * $1.75 = $<<9*1.75=15.75>>15.75.
Melvin needs to use $2 notes to buy the pencils.
To find the least number of $2 notes, we divide the total cost by the value of each $2 note: $15.75 / $2 = <<15.75/2=7.875>>7.875.
Since Melvin cannot use a fraction of a $2 note, he needs to use 8 $2 notes to buy the pencils. Answer: \boxed{8}.