Question posted by Alicia from Singapore:

Alex is 14 years old. In four years time, he will be twice as old as Samuel. How old is Samuel now ?

Answer:

Step 1: Draw 3 equal boxes, 2 to represent Alex's age, 1 to represent Samuel's age.

Step 2: As these are the ages of Alex and Samuel in 4 years time, we need to count backwards by 4 years and reduce both rows of the model by 4 to show the present ages of both persons. The "?" then shows Samuel's present age.

Thus, Samuel is 5 years old now.