A riddle that leaves you scratching your head can only be solved by people with a high IQ in 30 seconds or less.
The ‘Crackwork Bridge’ test is a scenario where four people attempt to cross a crumbling bridge at night, but only have one flashlight between them.
The bridge can only support two people at a time and it is too dangerous to cross without light.
The puzzle challenges participants to figure out the quickest way for all four to cross the bridge.
The rickety bridge test asks participants to answer the question of how a group of four people can cross at night when they only have a flashlight. Many quickly assume that the answer is simple, but the puzzle requires participants to ignore their initial answer by rationalizing the answer.
‘The bridge is too old, so only two people can cross it at a time. They only have one flashlight.
‘Each one takes 1, 2, 5 and 10 minutes to cross the bridge, and they always go at the pace of the slowest (if they cross A and B, it will take 2 minutes).
‘What is the minimum time needed for the four of them to cross the bridge?’
The Geeks for Geeks organization, which published The question provided a clue and told readers that they cannot walk around the bridge and shine the flashlight from the other end.
For those who tried to solve the problem quickly in the allotted time, the organization warned that the answer is not in 21 minutes.
Most people would think to use the fastest person who can cross in just one minute to transport everyone else across the bridge, but Geeks for Geeks warned that’s a mistake.
If the one-minute person were to guide each person, one at a time, the problem would look like this: 10 + 1 + 7 + 1 + 2 = 21 minutes.
“That would make this question easy even as a warm-up question,” Geeks for Geeks shared.
There is a quick way to get all four people across the rickety bridge, but to do so, readers must find a way to prevent 10 and 7 from crossing the bridge together first, since they are the slowest of the group.
There is a faster way to get all four people across, but to do so the readers must find a way to prevent 10 and 7 from crossing the bridge together first, since they are the slowest of the group.
If they were to cross together, one of them would have to go back to the other side of the bridge to retrieve another person.
To solve this problem, one and two will have to cross the bridge first, and two will have to return to the other side.
Then seven and ten crosses together, allowing the one minute person to return with the flashlight and take the two minute person back to the other side.
Total time: 2 + 2 + 10 + 1 + 2 = 17 minutes.
These types of math puzzles help promote stimulation in the brain which can help people develop visual and spatial reasoning skills.
It requires the individual to use logical thinking to correctly answer the question, which strengthens the connections between the person’s brain cells, improves their mental speed, and can improve short-term memory.
Puzzles have also been shown to increase a person’s intelligence level, with one study finding that those who work on challenging puzzles for at least 25 minutes each day can improve their IQ by up to four points.