How to set full view in for in the remaining area

Question

For example

I have a div.

i put the title in it

And under the title im gonna make full box on the remaining div area.

Can you explain

Answer 1

You nest another div inside that or calculate your stuff with maths.

Answer 2

Then you can do it dynamically with javascript.

Answer 3

Valen.H. ~ if i calculate with math, sometime im using "%" and sometime im using Pixel, it has different unit.