Question

Suppose you are given a bottle of water and three beakers. One of the beakers holds 30mL, one holds 40mL, and the largest of three beakers holds 200mL when full. There aren't any markings on any of the beakers. Describe how you could put exactly 20 mL of water in the large beaker without using any other equipment.

Answer 1

you can fill the 40 ml beaker, then empty it into the 30 ml beaker. you should be left with 10 ml in the beaker, pour this into the 200 ml beaker
repeat this and you should have 20 ml in the 200ml beaker

Answer 2

Fill the 200mL beaker all of the way. Using the water in that beaker, fill and pour out the 30mL twice and the 40mL three times. You should be left with 20mL in the 200mL beaker.