KNOXVILLE, Tenn. (WVLT) - For Kim Callahan, it's a numbers game.
She has been a teacher at Fulton High School for seven years. No matter how she breaks it down, one thing isn't adding up.
"Getting into some of the harder algebra concepts, they need the graphing calculator and see the graphs and see the concepts," said Callahan.
She teaches four classes, a total of more than 70 students, but only had enough calculators for one class to use at a time.
Because the calculators cost more than $100 on average, most of her students do not own their own which has caused Callahan to struggle to assign homework to all of her classes on the same night.
"A lot of them every day were asking if they could bring a calculator home and I'd say I'm sorry I need it for the next class or I need it the next day," she said. "If I only have 30 calculators to check out how do I decide who gets one and who doesn't?"
Students like Alexis Davis, who doesn't own her own calculator, has tried to make it work without one.
"I use the one online and it does basically the same thing, it just doesn't graph it," said Davis.
Callahan launched a campaign on social media and DonorsChoose.Org collecting used calculators or raising the more than $2,000 to cover the cost of 30 new ones.
"I've had people from Utah ship me calculators, from Atlanta ship me calculators, I met someone at Starbucks randomly who saw it on social media," she said.
A math problem that doesn't take a calculator to figure out.
Used calculators can be donated to Fulton High School.