The number is 23.94 and you want to round it to the nearest tenth. For this you examine the 100th place. It is 4. So the answer is 23.9
The rule is that you add one to the digit position to which you want to round to if the next less significant digit is 5 or more, otherwise leave it alone.
If the number was 23.95, then by adding 1 to 23.9, the answer becomes 24.0
2400
It is 232.4 when rounded to the nearest tenth
It is then 20.2 when rounded to the nearest tenth
10.5
33.8
2400
It is then 52.8 when rounded to the nearest tenth
It is then 56.5 when rounded to the nearest tenth
It is 232.4 when rounded to the nearest tenth
It is then 20.2 when rounded to the nearest tenth
It is 0.8 when rounded to the nearest tenth
4.4
10775.9
2.7
54.4
28.6
965.4