Question

how many national no. are there between 144 and 169

Answer 1

Well there are many rational numbers between 144 and 169.

You can find them by this method:

Multiply: Img 1 (1st fraction)
AND
Multiply: Img 2 (2nd fraction)

So the fractions will be: Img 3  ( 1st and 2nd respectively)

Therefore, you can write any of the fractions between these two fractions as your answer.