Escape from Deserted Island

You are stranded on a small deserted island. From the highest point on the island, you can see ships off in the distance but so far they have not seen your signal fires. You have built a raft and your plan is to paddle out to the shipping lane to get rescued. For water, you are going to pull a string of coconuts behind you and drink the coconut milk when needed.

The coconuts are about 40 cm in diameter and the liquid endosperm compartment is about 1/5 the diameter of the coconut. In the coconuts you've found, the hole is about 3/4 full with water. You plan to be gone for six days and you need about 3 liters of water each day.  How many coconuts should you bring with you?

Hints:

• For volume of a sphere:  v = 4/3*π*r³, where v = volume and r = radius
• 1 mL = 1 cm³
• Watch out for the coconut crabs!