A head-scratching brain teaser can only be solved by people with a high IQ in 30 seconds or less.
The 'Rickety Bridge' test is a scenario of four people trying to cross a dilapidated bridge at night, but only have one flash light between them.
The bridge can only support two people at a time and is too dangerous to cross without a light.
The puzzle challenges people to figure out the fastest way for all four to cross the bridge.
'The bridge is too old, so only two people can cross it at the same time. They only have one flashlight.
'They each take 1,2,5 and 10 minutes to cross the bridge, and they always go with the slower person's pace (if A and B are crossing, it'll take 2 minutes).
'What is the shortest time needed for all four of them to cross the bridge?'
The Geeks for Geeks organization, which published the question, provided a clue and told readers that they can't go around the bridge and shine the flashlight from the other end.
For those who quickly tried to solve the problem in the allotted timeframe, the organization warned that the answer is not 21 minutes.
Most people would think to use the fastest person who can make it across in just one minute to ferry the others across the bridge, but Geeks for Geeks warned that's wrong.
If the one-minute person guided each person across, one at a time, the problem would look like: 10 + 1 +7 + 1 + 2 = 21 minutes.
'That would make this question simple even as a warm-up question,' Geeks for Geeks shared.
There is a quicker way to get all four people across, but to do so, readers need to find a way to get around 10 and seven crossing the bridge together first, as they are the slowest among the group.
If they were to cross together, one of them would need to return to the other side of the bridge to retrieve another person.
To get around this issue, one and two will need to cross the bridge first, and two will need to return to the other side.
Then, seven and 10 crosses together, allowing the one-minute person to return with the flashlight and bring the two-minute person back to the other side.
The total time: 2 + 2 + 10 + 1 + 2 = 17 minutes.
These types of math brain teasers help promote stimulation in the brain that can help people build visual and spatial reasoning skills.
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.
