Elizabeth buys a notebook that has
109 pages. She completes her assignments in
seven pages. How many blank pages are left in
This is a subtraction problem. Elizabeth has 109 pages in her
notebook to begin with. And she uses seven pages to
complete her assignments. To find out how many pages she has
left in her notebook, we need to subtract seven from 109.
Did you notice that we’re
subtracting a one-digit number from a three-digit number? We can start by first subtracting
the ones. Seven only has a ones digit, so we
just need to subtract seven ones from our nine ones. We need to start at the number 109
and count back in ones seven times. One, two, three, four, five, six,
seven. 109, 108, 107, 106, 105, 104, 103,
102. If Elizabeth’s notebook has 109
pages and she uses seven pages, there will be 102 pages left in her notebook. 109 subtract seven equals 102.