Girls account for 3/8 of the fifth grade math interest group in a school, and then four girls are added, which is exactly 4/9 of the whole group. How many people are there in the group now?

Solution 1: Arithmetic method

The unit for boys is "1".

It turned out that the number of boys was 5/8 of the whole group, and later it was 5/9 of the whole group.

At first, the number of girls was three fifths of that of boys, and later, the number of girls was four fifths of that of boys.

So the number of boys is: 4/5-3/5 = 20.

Now the group size is: 20÷5/9=36 people.

Solution 2: Equation Method

Form the primitive group of x people.

3/8x+4=4/9(x+4)

x=32

So now there are 32+4=36 people in the group.