MINNEAPOLIS (WCCO) — Every Friday, we tackle a bunch of viewers’ burning questions. This week, Heather Brown explores gas prices, strange structures in the Mississippi River and gray hair.

Dave from Hammond and Alec from Prior Lake want to know: Why is gas priced at 9/10th of cent?

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“It’s called off pricing and the historical reason is that there is a presumption that people truncate when paying attention to price,” Akshay Rao, the Chair of the Marketing Department at the Carlson School of Management, said. “They don’t attend to the last couple of digits and, as a result, they have an illusion that they’re paying a price that is lower than they’re actually paying.”

Rao says this odd pricing is used for many kinds of products that end with a 5 or 9 in price. As for why gas ends with tenths of a cent, Rao says it’s a cultural artifact.

“Someone started to do it and now nobody want to stop doing it just in case there’s an adverse consequence to doing that,” Rao said.

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Rob walks his dog, Wilson, along the Mississippi River in Minneapolis just south of the Plymouth Avenue Bridge. During the walk, he sees three large round circular concrete structures in the water. He wants to know: What are they?

(credit: CBS)

(credit: CBS)

According to Lee Nelson, president of Upper River Services, these structures are old mooring cells. They were a place where barges could tie up as they wait for the lock. Nelson says barges don’t use them much anymore because there’s less traffic on the river and there’s better scheduling of when and where barges travel.

Andrea from South Minneapolis asks: Why does our hair turn gray when we get older?

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Each of are our hair follicles have pigment cells that produce melanin, which gives our hair its color. As we get older, those pigment cells die off, which produces less melanin, and, ultimately, less color.

Heather Brown