LinuxQuestions.org - simple read $a / grep question

Hi,
I wanted to write a simple script to kill a particular program.
My question is as follows:
why does 'ps ax | grep $1' work without any problems
and 'ps ax | grep $number' returns errors with usage or grep?

Code:

#!/bin/bash



E_BADARGS=65

if [ -z "$1" ]    # Check for argument to script.

then

  echo "Usage: `basename $0` program_you_want_to_kill"

  exit $E_BADARGS

fi



echo "Type the number of the process you want to kill: "

ps ax | grep $1

echo " "

echo "No of process you want to kill: "

read $number

echo $number

ps ax | grep $number

I also tried
ps ax | grep `echo $number`
ps ax | grep $(echo $number)

thanks