Only people with highest IQs can solve 'rickety bridge' brainteaser in under 30 seconds

A complicated brain teaser can only be solved by people with a high IQ in 30 seconds or less .

The rickety bridge test is a scenario involving four people attempting to cross a bridge at night, but they only have one torch between them. Each person takes a specific amount of time to cross the bridge and the bridge can only support two people at a time.

The challenge is to figure out the fastest way for all four to cross the bridge. The people each take 1min, 2 mins, 7 mins, and 10 mins, and the question is what is the shortest time needed for all four of them to cross the bridge? The answer might surprise you.

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The most obvious solution people will think of is to use the fastest person to guide everyone else across, add everyone's times together, making it 21 total minutes to get across the bridge. "That would make this question simple even as a warm-up question," the Geeks for Geeks organization, which published the question, said.

"To reduce the amount of time, we should find a way for 10 and 7 to go together as they are the slowest among all these," they said. "If they cross together, then we need one of them to come back to get the others. That would not be ideal." A work around to that would be having one waiting on the other side to bring the torch back, according to the organization.

One and two will need to cross the bridge first, and two will need to return to the other side. Then, seven and 10 cross together, allowing the one-minute person to return with the flashlight and bring the two-minute person back to the other side. Making the total time: 2 + 2 + 10 + 1 + 2 = 17 minutes.

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Mathematical brain teasers such as these can help promote stimulation in the brain that can help people build visual and spatial reasoning skills, DailyMail.com reported. "It requires the individual to use logical thinking to answer the question correctly which reinforces the connections between the person's brain cells, improves their mental speed, and can improve short-term memory."

Brain teasers have also been proven to increase a person's intelligence level, and a study found that those who work on challenging puzzles for at least 25 minutes each day can improve their IQ by up to four points.