When 13-year-old Lindsey Freitag heard she had to come up with a math project for school, she said she wanted to do one where she could make a difference for others.

For her project, titled “How can I make an impact?” Freitag crocheted as many children’s hats as she could in a 12-hour span.

She ended up making 14 hats in an average time of about 76 minutes each, and each hat cost 46 cents to make.

Then she calculated how many children in Minnesota under 5 are living in poverty. Using that number — 345,250 — she figured out how long it would take her to make hats for each of those children based off of the time it took her to make each of the 14 hats.

“If I kept crocheting and never stopped, it would take 3,003 days,” she said.

Freitag, who has been crocheting since she was 6, was one of more than 100 seventh-grade students at Southwest Middle School who presented their projects Wednesday during the 10th annual math fair.

“I want to spread out the word that making a difference isn’t as hard as people think,” she said.

Projects were open to the public starting at 8:45 a.m., with awards given out to five students following the judging.

Marci Maier, a Southwest seventh-grade pre-algebra teacher who helped organize the event, said the fair gets students to look at how math can make a difference in real life.

“It is important to know what the textbooks teach about math, but if students can’t apply it to real life, then we haven’t succeeded,” Maier said. “One of the goals of the math fair is to get students to look at how math can make a difference to society. It also gets them involved in the community outside their classroom.”

This year’s projects ranged from topics such as pets and food to sports, schools and travel.

Because her family was planning on taking a trip to Disney World, 13-year-old Ashley Holl completed a project on whether it is cheaper to book a trip on your own or to go through a travel agent.

Holl said she thought it would cost less to go through a travel agent.

She planned a trip with an agent from Four Seasons Travel and then went online to plan one through travel Web sites such as Travelocity and Orbitz.

In the end, she concluded it was cheaper to plan a trip with the travel agent, plus you can get insurance on your flight tickets, too, she said.

First: Sara Sanderson, “Is it cheaper to fix a car or buy a new one?”

Second: Lindsey Freitag, “How can I make an impact?”

Third: Tim Furland, “How much it costs to skate in ’08”

Fourth: Ashley Holl, “Is it cheaper to book a trip on your own or through a travel agency?”

Fifth: Brooke Hanson, “What type of birthday party is the least expensive?”

Planning a trip online also can have its problems with the increase in Internet fraud, Holl said.

Twelve-year-old Caycee Gilbertson, calculated whether it would be cheaper to go to Harvard University or Princeton University.

She went to both university’s Web sites, used math to calculate the costs and then multiplied that by four, for the number of years a person typically attends.

She found out that Harvard was the more expensive of the two universities by a few thousand dollars.

Gilbertson said she decided to do that project because she wants to go to law school someday. While conducting the project, she also learned that Harvard is the older institution and that both Harvard and Princeton are Ivy League schools.

The first math fair was held at Southwest in 2000. Since, the fair has consistently involved between 50 and 90 students.