Math brain teaser.... (1 Viewer)

[Outbackjack]

Saw this today, and I have to say it stumped me for a while......seemed easy, but frustrated me as I couldn’t solve it. FINALLY figured it out, but it wasn’t easy ??

I thought I’d throw it out there for fun....

Family of four needs to get through a cave through a mountain.
They have to have a light, and the torch has exactly 12 minutes of burn time.
The passage is narrow and can only fit 2 people at a time.
It takes them the following times to get through......
Dad (1 min) Mom (2 min) Sister (4 min) Brother (5 min).

How can it be done?

 

[Charlie Brizzown]

Two people walk next to each other, the other two people walk behind them. Five minute trip.

Don't go changing the rules after the fact.

 

[Grumpy Old Manatee]

They all have cell phones with flashlight apps and more than enough battery life to make the 5min (max) trek. No need to bother with the torch.

 

[Zack Lee]

Sacrifice the baby brother.

 

[UndeadSnoopy]

The answer is three.

You're welcome.

 

[Zack Lee]

Dad takes mom across. Then he goes back and gives the kids the lantern and they cross together. Then mom goes back and gets dad.

2min plus 1 min return
5 min plus 2 min return
2 min for mom and dad.

 

[Madmarsha]

What is: Who cares?

 

[Zack Lee]

In my answer above I assumed since it’s math that there are obscure rules like there isn’t enough light for a second row of people to see and dad can’t go through without a lantern because of the Blair witch. So return Trips have to be factored in.
It’s obvious brother and sister must travel together and equally obvious that neither can be part of a return trip. So they travel second trip with someone already on the other side for the return.

 

[tomwaits]

 

[Zack Lee]

“They can all float across” - PW

 

[boutrous]

Dad takes Brother 5 mins
Dad returns 1 min
Dad takes Daughter 4 mins
Dad returns 1 min
Dad kisses Mom goodbye and leaves her 1 min

5 + 1 = 6
6 + 4 = 10
10 + 1 = 11
11 + 1 = 12

 

[Outbackjack]

Sister and brother go through together first.
Dad goes through to pick up the torch and returns.
Mom and Dad go through.

dad can’t get through initially without torch

 

[Outbackjack]

Dad takes mom across. Then he goes back and gives the kids the lantern and they cross together. Then mom goes back and gets dad.

2min plus 1 min return
5 min plus 2 min return
2 min for mom and dad.

Bingo.
Impressive.

 

[Zack Lee]

Bingo.
Impressive.

career aptitude tests said I would excel in shuttling people through dark crevices. I didn’t understand it until now.

 

[Bill]

What is: Who cares?

It's my guess that you're not much for spelunking.
No one is going to call you a cave woman.