Primary School Maths - Topic # 1 Average
This posting is meant for all primary school students. If you have children going to Primary School, please help them out by getting them to read this. Or, better still, go through this with them.
IMPORTANT LESSON:
To find the average, use the formula AVERAGE = Total Amount / (divided by Total No. of Items.
https://youtu.be/95h7qAkz5QY
Calculating an average is a simple process that involves adding numbers together and dividing by the number of items that were added together. Find out how to determine that the average of three, four and eight is five with help from a math teacher in this free video series on math help and lessons.
Expert: Jimmy Chang
Bio: Jimmy Chang has been a math teacher at St. Pete College for nearly a decade. He has a master’s degree in math, and his specialties include calculus, algebra, liberal arts, math, and trigonometry.
Filmmaker: Christopher Rokosz
EXAMPLE 1: Find the average of 3, 7, 9 and 11.
No. of items = 4
Total Amount = 3 + 7 + 9 + 11 = 30
Average = 30 divided by 4 = 7.50
EXAMPLE 2: Find the average ratings of five uber drivers rated 4, 4, 3, 0, 1
Total ratings = 4 + 4 + 3 + 0 + 1 = 12
Total number of drivers = 5
Average ratings = 12 divided by 5 = 2.40
EXAMPLE 3: George drank 4.2 liters of milk in one week. What is his average consumption per day in milliliters?
Total consumption in 7 days = 4.2 litres of 4,200 milliliters
Total number of days = 7
Average = 4200.00 divided by 7
= 600.00 milliliters.
What would be the answer if George consumes 4.50 liters in the week?
Answer: 4500.00 divided by 7
= 642.857 liters The answer is given to three decimal places.
EXAMPLE 4: Five girls collected donations for the Red Cross and their collected amounts are $45.00, $21.50, $38.25, $17.10, $26.15. What is their average collection?
Total money collected = $45.00 + $21.50 + $38.25 + $17.10 + $26.15
Total: $148.00
Divide this total by five girls
Average = $ 29.60 per girl.
EXAMPLE 5: The weight or mass of four boys are: 30 kg, 42 kg, 48 kg and 38 kg. What is their average weight?
Total weight of the four boys = 158
Divide this by 4, the average weight is 39.50 kg.
EXAMPLE 6: The average score of eight students in a maths test is 65 out of 100. What is their total score?
Answer: Total score = Average score multiplied by total number of students
= 65 x 8 = 520.
EXAMPLE 7: The average of two numbers is 62. If one number is 80, what is the other number?
Average of 2 numbers = 62
Total for the 2 numbers = 124
One number is 80
The other number is 124 - 80 = 44,
EXAMPLE 7: The average number of students in five classes is 35. If the sum of the number of students in four classes is 135, how many students are there in the last class?
Average of five classes = 35
Total number of students for the five classes = 35 x 5 = 175
Total number of students in four classes = 135
So number of students in the last class = 175 - 135 = 40
EXERCISES:
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- Find the average of each of the following set of numbers:
(a) 45, 72, 81
(b) 2.5 gram, 5.6 g, 4.2 g, 2.5 g
(c) 125 millilitres, 145 ml, 235 ml, 200 ml, 172 ml, 380 ml
(d) 5 kg 150 g; 11 kg 50 g; 16 kg 350 g. [Answer in kg.]
(e) 6 m 90 cm; 5 m 20 cm; 6 m 35 cm; 7m; 2 m 85 cm [Answer in cm]
2. A man walks every day. Last week he walked 12 km on Monday,
15 km on Tuesday,
10 km on Wednesday,
8 km on Thursday,
13 km on Friday,
21 km on Saturday
and took a rest on Sunday.
What was the average distance he had walked for the six days, Monday through to Saturday? What was the average distance he had walked for the week?
3. The average height of eight men is 1.72 meters. If the average height of five of these eight men is 1.68 meters, what is the average height of the remaining three men?
4. James runs 200 meters in 25.1 seconds on average. If his recorded time trials for the last five trials were:
24.5 s;
23.8 s;
24.6 s;
25.1 s;
and 25.8 s;
What was his average speed for these five time-trials? How much faster or slower had he performed compared to his normal average speed?
5. Four groups of 40 charity workers collected donations from the public at Queens Street. The following are their collection results during the first hour.
Group 1 - 9 workers collected $28.00
Group 2 - 10 workers collected $54.00
Group 3 - 8 workers collected $62.00
Group 4 - ??? workers collected $ ???.??
(a) How many workers are there in Group 4?
(b) If the average collected by all four groups is $54.00, find the amount collected by Group 4.
(c) What is the average amount collected by each group?
6. The average volume of water in Pail P and Pail Q is 4.25 liters. The total volume of water in Pails R and S is 8.09 liters. Find the average volume of water in the four Pails P, Q, R and S.
7. The average of two numbers is 38. If the difference between the two numbers is 8, what are these two numbers?
8. The ratio of my age to my brother’s age is 5:2. If I am 6 years older than my brother, in how many years’ time will our average age be 16 years?
9. There are five numbers. The average of the lowest two numbers is 32. The average of the lowest three numbers is 66 and the average of the lowest four numbers is 114. If the average of all five numbers is 170, what are these five numbers?
10. Fill in the blanks in the following boxes:
SET OF NUMBERS No. of Data in Set Total Value Average Value
30, 50, _____ , 90 4 215 _______
1, 3, 6, 9, ______ ______ ______ 5
2, 9, _____, 12, 8 ______ ______ 10
_____, 154, 112 3 400 _______
1.5, 2.5, 3.5, ____, 5.5 ______ 30 _______
3, 0, 2, 8, 0, _____ ______ 18 _______
15, 22, _____ ______ ______ 18
Set numbers not stated 4 (numbers) ______ 25 (average)
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DESIGN your own further exercises for your Primary School children by using the formats of above questions and replacing the numbers given. Do this for ten consecutive days and they will then be experts in this topic.