7. Castaways and Coconuts
At number 7 on our list of math problem-solving activities for middle school we have the following problem – three sailors were stuck on a deserted island that was also home to a hoard of monkeys. The sailors worked all day to collect coconuts but were too tired that night to count them. Instead, they agreed to divide them equally the next day. During the night, one of the sailors who couldn’t sleep decided to take his share of the coconuts. When he did so, he found that the coconuts could be divided into three equal piles, with one coconut left over, which he gave to the monkeys. Having done this, he put his coconuts in a pile down the beach and left the rest in one pile near where the others were sleeping. Later that night, sailor number two woke up and also decided to take the coconuts that belonged to him. He was able to make three equal piles as well with one coconut remaining, which he threw to the monkeys. A bit later, the final sailor woke up and did the same thing as the previous two. In the morning, all three sailors noticed that the pile was much smaller, but each thought that he knew why and said nothing. When they then split up what remained of the original pile of coconuts equally, each sailor received seven and one was left over, which they threw to the monkeys. How many coconuts were in the original pile?
Just as in the mango problem, students can work backward from the initial amount of 7 each by multiplying by 3 and adding 1 to wind up with 22. From there, following the information provided in the problem will ultimately yield an answer of 79.
Pixabay/Public Domain
