Hi there,
I am trying to find out the mean height in this case but there are no displayed data from the sample here. It simplies says:

The same mean height for a class of 30 students was 170 cm. The 20 male students in the class have a mean height of 180 cm. What is the mean height of female students in the class?

How would I work this out in a mathematical equation without trial and error.
Thank you

Mean is the same thing as ratio.

The mean height of 30 students = 170 cm.

You therefore have a series of height, when added together giving a certain value, and when divided by 30 gives 170.

Let the total height os the students be x, that of boys be y, that of girls be z and the mean height for girls be m.

Therefore, the mean here is given by \frac{x}{30} = 170

The mean for boys is \frac{y}{20} = 180

The mean for boys is \frac{z}{10} = m

To have the total of all the students heights is x. Subtract the total height for boys, y, from that to obtain the total heights for girls, z. Divide that value by 10 to have m, the mean height for girls

Thank you very much. Much appreciated

You're welcomed! :D