Answer:
17 years
Step-by-step explanation:
The sum of the ages of the 5 people in the room is : 23 + 24 + 17 + 24 + 21 = 109
If the mean age of 6 people is 21, then the sum of the ages of the 6 people is: 6 x 21 = 126 years
To calculate the age of the peron who entered the room, subtract the sum of the ages of the initial 5 people from the sum of the ages of the 6 people:
126 - 109 = 17
So the age of the peron who entered the room is 17 years.
