How the four people can manage to cross has been properly explained and the minimum number of crossing required for the boat is 7 times
From the question,
Four people want to cross the river and there is only one boat available, and the boat can only carry a maximum of 200 pounds.
The weight of the four people are 109, 170, 110, and 90 pounds.
For them to cross the river,
Two persons (the ones weighing 109 and 90 pounds) will first board on the boat. When they get to the other side of the river, the person weighing 109 pounds will drop and the person weighing 90 pounds will return the boat.
Here, total weight = 199 pounds
Then, one person (the one weighing 170) will now board on the boat. He alone will cross the river and the person weighing 109 pounds, who was at the other side of the river before will return the boat.
Here, total weight = 170 pounds
Now, two persons (the ones weighing 110 and 90 pounds) will board. When they get to the other side of the river, the person weighing 110 pounds will drop and the person weighing 90 pounds will return the boat to pick the remaining person weighing 109 pounds.
Here, total weight = 200 pounds
Finally, the persons weighing 90 and 109 pounds will then board on the boat and cross the river to the other side.
Here, total weight = 199 pounds
From above, the minimum number of crossing required for the boat is 7 times
How the four people can manage to cross has been properly explained and the minimum number of crossing required for the boat is 7 times
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