It is a well known fact that during a total solar eclipes the disc of the moon almost completely covers the disc of the sun. From this fact and from the information you can gather from Solved Examples 3 and 4 on page 1//44, determine the approximate diameter of the moon.

Explanation

Distance (ME) of earth from the moon `=3.8xx10^(8)m`
Distance (SE) of earth from the sun `=1.496xx10^(11)m`
Diameter of the sun `=PQ=1.38xx10^(9)m`
During solar eclipse, the disc of the moon completely covers the disc of the sun.
`trianglePQE" and RSE` are similar to each other.
`(PQ)/(RS)=(SE)/(ME)`
`(1.38xx10^(9))/(RS)=(1.496xx10^(11))/(3.8xx10^(8))`
`implies RS= (1.38xx10^(9)xx3.8xx10^(8))/(1.496xx10^(11))`
`=3.50xx10^(6)m`.