Find the shortest distance
A 120 wire cable has been laid firmly underground between two telephone exchanges located 10km apart.
Unfortunately after the cable was laid it was discovered to be the wrong type, the problem is the individual wires are not labeled. There is no visual way of knowing which wire is which and thus connections at either end is not immediately possible.
You are a trainee technician and your boss has asked you to identify and label the wires at both ends without ripping it all up. You have no transport and only a battery and light bulb to test continuity. You do have tape and pen for labeling the wires.
What is the shortest distance in kilometers you will need to walk to correctly identify and label each wire?
20.
At one end label a wire “A”. Then join two wire and label them both “B’, then tie three (not already joined) wires together and call them each “C”….continue until all the wires are joined together in groups of 1, 2, 3, 4, 5, etc….for a 120 strand cable. NOTES that the largest group will have 15 wires.
Now walk to the other end.
Using a (battery and light bulb) it is now possible, for example, to find the wire that wasn’t joined to any of the others. It is similarly possible to find which wires are in a pair, which is joined in a group of 3, etc. Each time a group is found the technician should label it with the letter for the group, so the single wire is labeled ‘a’, the pair are each labeled “A”, etc….this now matches the other end…..the letters will go up to “O”. Now take “A”, “B”, up to “O” and join them together in a group and label each one with “15”, so we have cable “A15”, “B15′, “C15”, up to “O15”. Take the second and last “B'”wire and
join it with a remaining “C”, “D”, up to “O” and label these each “14′ so we have “B14”, “C14”, up to “O14”. Repeat this until at the end there will be a single “O” cabled labeled “O1”.
Now walk to the other end.
Now untie all the old connections and identify the group labeled “1”, “2”, “3” …”15″ at which point each wire at each end has a unique classification.
Alternative solution from citrog:
First, tie the 120 wires together randomly in 60 pairs. Next, go to the far end, randomly label any wire 1, and connect the battery to it. Test which other wire is tied to it at the starting end, and label that wire 2. Then pick another wire other than 1 or 2, label it 3, and tie it to 2, so now the battery is connected to 1, which is tied to 2 at the other end, which is tied to 3 at the end you’re at. Now test which wire is tied to 3 at the other end, and label that 4, etc. What you will wind up with is all 120 wires tied to each other in a continuous sequence. Then go back to the end you started at, leaving the battery behind, connected to wire 1. Before you untie all the wires at the starting point, label each wire so that you know which wire was paired with which. Now with all the wires untied at the starting point, test which wire is connected to the battery, and label that 1. Whichever wire was in the same pair as 1, label that 2, and then tie 1 and 2 back together. Now you can find 3, because it’s tied to 2 on the far end. Once you find 3, label the wire it was tied to 4, etc. This assumes that the resistance of the wire is small enough that the battery will still light the bulb across 12,000 km of wire.
Your Answer
More puzzles to try-
Divide 30 by 1/2 and add ten Tricky Math Puzzle
Divide 30 by 1/2 and add ten. What is the answer?Read More »Reading without Light
Jessica is telling her friends this story and asks them to guess if it’s the truth or a lie: “There ...Read More »12345 is an Actor
12345 a famous South Indian actor 567 is a path in jumbled form 8 & 10 are same letters 9 ...Read More »Cheater husband puzzle – ANALYZE SITUATION
There is a town named Panem. The town is well built and have every facility available to the citizens. It ...Read More »Magic Algebra Fun
You are given with the following sum. Each of the letters can be decoded as a digit. If we tell ...Read More »Horseshoe tricky riddle
If the horseshoe is in the barn, is it March?Read More »Egg and Hen
One fine day, an intellectual man came to the emperor’s court with the aim of testing Birbal’s wittiness. In order ...Read More »Something with head and tail in jungle puzzle
An explorer goes on an exposition in the jungle. He sets up camp in the middle of the jungle. The ...Read More »Complete The Cube
Below is a cube which has been opened up. Fill in the missing boxes.Read More »The New Year Riddle
Name the most recent year in which New Years came before Christmas?Read More »Find the thief in the puzzle below riddle
Hi Mr. Detective, We have a thief in this picture below, help us to find?Read More »What if the pizza was worth $11?
Rihana, Peeta, and Logan order a pizza for $10. Out of the three, Rihana and Peeta were quite hungry and ...Read More »Lost Brother riddle
A man is able to contact his long lost brother who has never met. They agree to meet. When the ...Read More »Who was buried ?
Who was buried in Grant’s Tomb?Read More »Game of Kids riddle
It’s always 1 to 6, it’s always 15 to 20, it’s always 5, but it’s never 21, unless it’s flying. ...Read More »Black when clean riddle
I am black when clean and white when dirty. What am I?Read More »How would you have handled the situation?
My friend Shuba works in a post office and she sells stamps. One day a man walked in and kept ...Read More »2 men catch 2 fish in 2 minutes
2 men catch 2 fish in 2 minutes. At this rate, how many men could catch 500 fish in 500 ...Read More »Mother Daughter age puzzle
Ten years back the age of the mother was 4 times of her daughter’s age and After ten years – mother’s ...Read More »Favorite States
What are the science teacher\’s favorite states?Read More »