There are multiple ways to measure the diameter of the moon. The following is one method. Your team should try to develop their own method to measure the diameter of the moon.
Using a plastic or metal washer of any size you can estimate the diamter of the moon. Hold the washer out an arm's lenght Sight the moon with one eye closed such that the moon is visible through the washer. Bring the washer slowly closer to the eye unitl the moon's circular surface just touches the inside circumference of the washer. Have a partner measure the distance from the washer to the eye. Record this in cm, then convert it to km. Measure the inside diameter of the washer, also record this in cm and convert it to km. The distance to the moon is 386200 km. Use the following proportion to determine the distance
diameter of moon (X)/distance to moon (km) = diameter of washer (km)/distance from eye to washer (km)
Remember to always check you answer. Always ask yourself does what you obtained make sense.