This problem can be solved by treating it like a

weighted average prooblem.

Let the average number of holidays/employee be x (the weighted average).

From the stem we know that the average number of holidays/CFA = x-5 and the average number of holidays/MBA = x+10.

Apppying the

teeter totter method (from MGMAT): Thus, the the total distance between x-5 and x+10 = 15.

x-5--------------------x-----------------------x+10

distance from x=5 , distance from x=10

As we want to determine the number of CFAs, we can use the above teeter totter to conclude CFAs make up \(\frac{10}{15}=\frac{2}{3}\)of the total number of employees.

Using the teeter totter is a great way to simplify and visualise. Moreover, this approach is quite fast and took me around 1.5 minutes.

Please hit Kudos if you liked this approach