There are a total of 10 counters.
Count how many counters have the number 3 written on them.
There are 6 counters with the number 3 written on them.
The probability that the number on the counter is 3 is given by
[tex]P(3)=\frac{6}{10}=\frac{3}{5}[/tex]
Now, count how many counters have the number 4 written on them.
There are 3 counters with the number 4 written on them.
The probability that the number on the counter is 4 is given by
[tex]P(4)=\frac{3}{10}[/tex]
Finally, the overall probability is (or means to add the probabilities)
[tex]P(3\: or\: 4)=\frac{3}{5}+\frac{3}{10}=\frac{2\cdot3+3}{10}=\frac{6+3}{10}=\frac{9}{10}[/tex]
Therefore, the probability that the number on the counter is 3 or 4 is 9/10
[tex]P(3\: or\: 4)=\frac{9}{10}=0.90[/tex]
