Bridge and torch problem : Four people come to a river in the night. There is a narrow bridge, but it can only hold two people at a time. They have one torch and, because it's night, the torch has to be used when crossing the bridge. Person A can cross the bridge in 1 minute, B in 2 minutes, C in 7 minutes, and D in 10 minutes. When two people cross the bridge together, they must move at the slower person's pace. What is the least time taken for them to get across the bridge?
Sukhi Sahu
5d
10 minute
Shiva Akash
7d
student at
Madras University
17 minutes
Anonymous
8d
Step 1: A+B go → 2
Step 2: A returns ← 1
Step 3: C+D go → 10
Step 4: B returns ← 2
Step 5: A+B go → 2
Total = 2 + 1 + 10 + 2 + 2 = 17 minutes
Aditya Patel
8d
Step 1: A+B go → 2
Step 2: A returns ← 1
Step 3: C+D go → 10
Step 4: B returns ← 2
Step 5: A+B go → 2
Total = 2 + 1 + 10 + 2 + 2 = 17 minutes
DIVYA GUPTA
12d
21 min because at a time two person can cross bridge first time = A and D go togather and ! will retun with tourch ( 10 +1 ) = 11 min sec time = A+C go togather and ! will retun with tourch ( 7 +1 ) =...read more
Dr. GOUTAM BANERJEE
15d
works at
11 minutes
Goutam Patar
15d
2+1+7+1+10=21(assume A return always for taken others)
Mr. Rupesh Dnyaneshwar Buwa
18d
23 min
Sandeep Gautam
18d
17 min
ctrlnova
19d
student at
University Department of Information and Communication Technology
21 mins
Anonymous
20d
currently not working
23min
shrinathdwivedi
24d
works at
Seaspeed Marine Services LLP
17 minutes
Megha Elsa
25d
17 minutes
Layma
27d
Last other two people can never crossed the bridge because first two people crossed the bridge with one torch now last two peoples haven't there torch so sorry for last two people 😔
cute sonali
27d
Minimum 17 minutes required
Raj Goswami
28d
15
Priya Vadivelan
28d
10
sagar Kevant
29d
17 minutes
Dhanush Srinivasan
1mo
17 minutes
Vvikas Biraree
1mo
17 mins
Riya
1mo
3+10+2=15
Avinash
1mo
17 minutes
Vaibhav Zemse
1mo
21
Sumit Kumar
1mo
Only 21 minutes
Sunil Kumar Pradhan
1mo
21
Suresh Rana
1mo
works at
12
Sathishkumar P
1mo
10 + 2 + 2 = 14
cuddlybhindi
1mo
ex -
10+1+1+7+1+1+2 = 23
Anonymous
1mo
21
cuddlybhindi
1mo
ex -
They need to move at slower pace when traveling together as it is dark so let's consider 1 minute as...read more
Anonymous
1mo
20
Senthil Kumar
1mo
21
Senthil Kumar
1mo
12 minutes
M RAVITEJA
1mo
17 minutes
rebeccah too
1mo
280 MINUTES
Anonymous
1mo
17
VINAYANADH.V.R
1mo
Answer is 17. A and B cross the bridge. A comes back. Time taken 3 minutes. Now B is on the other side.C and D cross the bridge. B comes back. Time taken 10 + 2 = 12 minutes. Now C and D are on the ot...read more
Mayur Jadhav
1mo
2 + 1 + 10 + 2 + 2 = 17 minutes
Thus, the least time required for all four people to cross is 17 minutes.
Anonymous
1mo
Answering 17 minutes a and b first cross the bridge in 2 minutes and a 1 minute again trouser balance 14 minutes in be and c slower they bridge cross in 10 minutes balance 4 minutes b again cross the ...read more
JEYA BELLA D
1mo
Answer is 17. A and B cross the bridge. A comes back. Time taken 3 minutes. Now B is on the other side.C and D cross the bridge. B comes back. Time taken 10 + 2 = 12 minutes. Now C and D are on the ot...read more
Sahil Thakur
1mo
student at
Rayat & Bahra Institute of Engineering & Bio-Technology, Kharar
answer is 17 because here is 4 people a and b cross the bridge together with the speed of <2> mint or unke pass torch bhi hai and then A baapis jaayega torch dene C or D ke pass speed <1> and then C o...read more
Kamrul Hoda
1mo
7mints
priti gupta
1mo
10 minutes
Anonymous
2mo
8 minutes
Anonymous
2mo
25 minutes
Anonymous
2mo
8
Anonymous
2mo
17 minutes
Pranav Gangurde
2mo
It will take 21 mins 10+1=10 (max time taken to cross bridge) 1=return time 7+1=7 (max time taken to cross bridge 2nd time) 1=return time 2 2+1=2 (max time taken to cross bridge 3rd time) 10+1+7+1+2=2...read more
sandeep ramini
2mo
Ans is 17 mins Initial Crossing Person A and Person B cross the bridge together, taking 2 minutes (since B is slower). The torch is now on the other side.Returning the Torch Person A returns with the ...read more
Vishal Soni
2mo
ex -
A and B cross (2 minutes): The fastest two go together. A returns (1 minute): The fastest person comes back with the torch. C and D cross (10 minutes): The slowest two go together. B returns (2 minute...read more
SUGANYA.G
2mo
17 mins
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