23
The mean (average)
Textbook: Part 1, lesson 23, pp. 72–74
GoalUnderstand the mean (arithmetic average) and calculate it.
New words
mean (average) · o‘rta arifmetikaverage value · o‘rtacha qiymatsum · yig‘indinumber of values · sonlar soni
Explanation
To find the mean of several numbers, divide their sum by how many numbers there are. For example, the mean of the marks 5, 4, 3, 5, 3 is (5 + 4 + 3 + 5 + 3) : 5 = 4. The mean lies between the smallest and the largest number. If the mean and the count are known, the sum is found by multiplying.
Worked examples
12, 15 and 9 pages: (12 + 15 + 9) : 3 = 36 : 3 = 12 pages.
If on average 7 problems were solved on each of 5 days, then 7 × 5 = 35 problems were solved in all.
Class activity
“Level it out”: each group gets a different number of cubes. Children share them equally to find the average per group and check with a calculation.
Practice
1
Find the mean of 8, 12, 10, 14, 6.
10
2
Shahzoda read for 20, 25, 30, 25 and 25 minutes on five days. How many minutes a day did she read on average?
25
3
The average mass of 4 pupils is 28 kg. What is their total mass in kg?
112
4
Three Grade 4 classes have 31, 35 and 33 pupils. What is the average number of pupils per class?
33