I have multiple options 1. depending on where the tunnel is my guess is they go around it. 2.they morph together and walk together. 3. its a short tunnel so they don't need to go 12 + more minutes. 4. there are torches on the wall that they can light on their way.
Dad and daughter go in first. When they get to the end daughter stays there. Time 5 min. Dad comes back Time 6 min. Dad does the same as daughter with son. Time 10 min. Dad comes back. 11 min. Mom goes with dad. Wait this isn't possible all of them together equals 13 minutes!
Wait I got it yes. First mom and dad â" 2 minutes. Dad comes back â" 3 minutes, both children go to mom â" 8 minutes. Mom brings torch back. They walk together.
Well anyway, Dad and daughter first(5min).Dad comes back and gives the torch to the others and returns (7min).They both go (mom and son)(4min). So (4+7min =11min) THAT MUST BE!
DAMN sorry, really sorry for double posting but i FOUND IT!
dad and mum(2min).Mum returns the torch to children and stays there(4min).Son and daughter pass(9min).Dad returns the torch to mum (+1min=10min)and they both go through(+2min=12min). This one is or i cannot think of anything else!!!!!!!!!