Haven't posted one of these in a while, but Alex Bellos had a fun little puzzle today that wasn't too mentally taxing:
As per usual, answers in spoilers, please.
Six friends – Babs, Charles, Hattie, Joan, Kenneth and Sid – are going camping in France.
They are travelling across the Channel on a magic carpet (of course) that can take only two people at a time. So, in order for everyone to get across there will need to be 9 trips in total from their starting point in England: 5 across carrying two people, and 4 returning carrying one person. (Magic carpets cannot fly with no one on board, which is why one person needs to travel back. All the friends are able to fly alone on the carpet if need be.)
The faster the carpet flies, the bumpier the ride. Babs can fly at a speed that gets her to France in 1 minute. Charles feels queasy at that speed: his maximum speed gets him to France in 5 minutes. The others can get to France without suffering debilitating travel sickness no faster than 6 mins (Hattie), 7 mins (Joan), 8 mins (Kenneth) and 12 mins (Sid).
1. What is the least amount of flying time, in minutes, required to get everyone from England to France without anyone suffering from queasiness? (When two people are on the carpet together, the crossing will take as long as it takes the slowest of the two.)
2. Let’s say that the friends’ tolerance for travel-sickness means that their fastest journeys take the following times: Babs (1 minute), Charles (3 mins), Hattie (7 mins), Joan (9 mins), Kenneth (11 mins) and Sid (13 mins).
Now what is the least time, in minutes, required to fly all friends to France?
Here’s a tip: the answer to question 1 is less than 45 minutes. And the answer to question 2 is less than the answer to 1.
They are travelling across the Channel on a magic carpet (of course) that can take only two people at a time. So, in order for everyone to get across there will need to be 9 trips in total from their starting point in England: 5 across carrying two people, and 4 returning carrying one person. (Magic carpets cannot fly with no one on board, which is why one person needs to travel back. All the friends are able to fly alone on the carpet if need be.)
The faster the carpet flies, the bumpier the ride. Babs can fly at a speed that gets her to France in 1 minute. Charles feels queasy at that speed: his maximum speed gets him to France in 5 minutes. The others can get to France without suffering debilitating travel sickness no faster than 6 mins (Hattie), 7 mins (Joan), 8 mins (Kenneth) and 12 mins (Sid).
1. What is the least amount of flying time, in minutes, required to get everyone from England to France without anyone suffering from queasiness? (When two people are on the carpet together, the crossing will take as long as it takes the slowest of the two.)
2. Let’s say that the friends’ tolerance for travel-sickness means that their fastest journeys take the following times: Babs (1 minute), Charles (3 mins), Hattie (7 mins), Joan (9 mins), Kenneth (11 mins) and Sid (13 mins).
Now what is the least time, in minutes, required to fly all friends to France?
Here’s a tip: the answer to question 1 is less than 45 minutes. And the answer to question 2 is less than the answer to 1.
As per usual, answers in spoilers, please.