Example (less than)

Author:
Lew W. S.
The tennis ball shown below can be put into the tube easily. What do you think is the size (diameter, in cm) of the tennis ball ? Let's use the letter d to represent the diameter of the tennis ball in centimetres (cm)  What are the possible values of d?
Image
If d = 6.8, then the tennis ball may just fit the tube but its not easily to put in or take out! So d could be 6.75, 6.7, or 6.6 or anything less than 6.8. How do we write "d is less than 6.8 cm" mathematically?   Well,    d < 6.8     We were asking for the possible values of d which will allow the tennis ball to be put into the tube easily. And the solution for d is :   d < 6.8