Monday: 18 squares
Tuesday: 18 + 7 = 25 squares
Wednesday:25 + 7 = 32 squares
Thursday: 32 + 7 = 39 squares
Friday: 39 + 7 = 46 squares.
This is called an arithmetic sequence. There is a faster way to do this with a formula.
The formula is a(n) = a1 + d(n-1), where
a1 is the first term (18 in this case),
d is the common difference, what you add or subtract to get the next number (7 in this case),
n is the term you want to find (5).
Plugging in our info into the equation,
a(n) = a1 + d(n-1)
a(5) =18 + 7(5-1)
a(5) = 18 + 28
a(5) = 46
