Playing for charity on Who Wants to Be a Millionaire last week, The Hills star and best-selling author Lauren Conrad proved she was up to the trivia test.

Appropriately, she was given a celebrity gossip question.

After she correctly identified the name of Prince William's girlfriend (Kate Middleton), LC's new foundation became $25,000 richer. What can't she do?

Check out the clip of Lauren Conrad on the show below ...

Lauren Conrad on Who Wants to Be a Millionaire

Sure, this wasn't the toughest mental task in history, but nor is making change for $7.50, which flummoxed Everybody Loves Raymond's Patricia Heaton.

Heaton received a number cruncher that had fourth-graders watching at home howling at the screen: "If a Euro is worth $1.50, five Euros is worth what?"

Her choices: 30 quarters, 50 dimes, 70 nickels or 90 pennies. Too hard, apparently. Lauren Conrad would've nailed this in about 10 seconds, we'd guess.

"I don't know, I have no idea," she said, and immediately elected to use the lifeline of calling her husband because he's European ... and he was no use.

Host Regis Philbin finally walked Heaton through the question and, through process of elimination and a few rounds of applause, they got the answer.

Check out her staggering lack of intelligence here ...