Question

answer the question plz​

Answer 1

$\huge \star{ \underline{ \underline{ \bf{ \red{A} \purple{n} \pink{s} \orange{w} \blue{e} \green{r}}}}} \star$

$\purple{: \implies{ \rm{ \red{24 }\: \green{minutes}}}}$

${ \rm{ \red{Step} \: \green{By} \: \pink{Step} \: \orange{Explantion} : }}$

Each person taking time

A - 1 min

B - 2 min

C - 7 min

D - 10 min

Given that

Maximum 2 people can cross the brigde (A pair)

Then,

A + B & A returning = 1 + 2 + 1 = 4 min

A + C & A returning = 1 + 7 + 1 = 9 min

A + D = 1 + 10 = 11 min

So, here

‘A’ person crossing the bridge for the last time

Now,

Adding all

4 + 9 + 11 = 24 min

Answer 2

Given:

• Time taken to cross the bridge by:

⟼ A- 1 min

⟼ B- 2 min

⟼ C- 7 min

⟼ D- 10 min

• People that cross the bridge must carry the lamp to see the way and they have 1 lamp
• At maximum, only 2 people can cross the bridge at a time
• A pair must walk together at the speed of slower person

To Find:

• Minimum time required by all 4 friends to cross the bridge

Solution:

Step 1:

Firstly, A and B should cross the bridge

Here, B is slower

Time taken by them= 2 min

Step 2:

Now, A should take the lamp back to his remaining 2 friends

Time taken by A= 1 min

Step 3:

Now, C and D should cross the bridge

Here, D is slower

Time taken by them= 10 min

Step 4:

Now, B should take the lamp back to friend A

Time taken by B= 2 min

Step 5:

Now, A and B should cross the bridge one last time

Here, B is slower

Time taken by them= 2 min

Total time taken= 2+1+10+2+2= 17min

Hence, total minimum time required by 4 friends to cross the bridge is 17 minutes.