There are 45 students in a class, 20 of whom have 2 siblings, 15 of whom have 1 sibling, while the rest have no siblings.
How many siblings do the students in the class have on average?
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There are 45 students in a class, 20 of whom have 2 siblings, 15 of whom have 1 sibling, while the rest have no siblings.
How many siblings do the students in the class have on average?
To solve this problem, we'll follow these steps:
Step 1: Determine the number of students with no siblings.
The problem provides us with the following information:
- 20 students have 2 siblings.
- 15 students have 1 sibling.
- Total number of students = 45.
The number of students with no siblings can be calculated as:
Number of students with no siblings = Total number of students - Students with 2 siblings - Students with 1 sibling.
Step 2: Calculate the total number of siblings.
The total number of siblings is calculated by summing the product of the number of siblings and the number of students in each category:
Total number of siblings = (2 siblings × 20 students) + (1 sibling × 15 students) + (0 siblings × 10 students)
Step 3: Use the weighted average formula.
The weighted average for the number of siblings per student is given by:
Average number of siblings =
Therefore, the students in the class have, on average, siblings.
siblings
Norbert buys some new clothes.
When he gets home, he decides to work out how much each outfit cost him on average.
What answer should he come up with?
That would give you the average of the sibling categories, not the average per student! You need to weight each category by how many students it represents.
Subtract the given groups from the total: 45 - 20 - 15 = 10 students with no siblings. Always check that your groups add up to the total!
A weighted average accounts for how frequently each value appears. Since 20 students have 2 siblings, the value '2' has more weight than '1' which only 15 students have.
Check what the problem asks for! In this case, rounds to 1.22 siblings (two decimal places is typical).
Yes! Averages can be decimals even when the original data contains only whole numbers. The average represents the typical value per student, not an actual count.
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