Comment by lucio

When you put two tables together, each table has 1/2 of the total number of kids. By having 2 tables, now you have 6 kids, so:

the original 1/3 in the first table becomes 1/6

the original 1/3 in the second table becomes 1/6

so adding the two tables means 2/6 are girls

She needs to explain 1/3 of 1/2 (fraction of a fraction) before using an example where she joins two units (two tables)