Q&A for How to Find the Average of a Group of Numbers

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The average of 4 numbers is 56. If the average of 3 of the numbers is 52, what is the 4th number?

Donagan

Top Answerer

The sum of the four numbers is 4 x 56. The sum of the three numbers is 3 x 52. The difference between the those two sums is the fourth number.

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If the average age of three brothers is 15, and two brothers are 15 and 12, how do I find the age of the third brother?

Community Answer

15 times 3 equals 45, 12 plus 15 equals 27, 45 minus 27 equals 18. The third brother's age is 18. Check: 15 plus 12 equals 27, 27 plus 18 equals 45, and 45 divided by 3 equals 15.

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How do I find the average of 4kg, 240g, and 167g?

Community Answer

To find the average, add all of the numbers in the set. In your case, 4000, because 1kg+1000g, 4000+240+167 = 4407. Then, because there are three numbers, divide by 3 4407/3 = 1469.

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If the average of four numbers is 72, and two of the numbers are 68 and 70, how do I find the average of the remaining numbers?

Community Answer

First find the total of the four numbers (72 x 4 = 288). Then find the total of the two numbers that are given to you (68 + 70 = 138). Then find the total of the two unknown numbers (288 - 138 = 150). Divide that number by 2 to find the average of the two unknowns: 150 / 2 = 75.

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How do I find the mean?

Donagan

Top Answerer

In mathematics, "mean" and "average" are the same thing.

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If the average height of four flowers is 25 cm, and three of them average 20 cm tall, how tall is the fourth flower?

Donagan

Top Answerer

Let x equal the he height of the fourth flower. For purposes of this solution, you can assume that the height of each of the other flowers is 20 (because their average is 20). Then (20 + 20 + 20 + x) ÷ 4 = 25, or (60 + x) ÷ 4 = 25. Multiply both sides of the equation by 4: 60 + x = 100, which means 4 = 40.

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The average age of 20 people was 35. A 55-year-old man was replaced by a 35-year-old man. What is the new average?

Donagan

Top Answerer

In the original group the total age was 20 x 35 = 700 years. The total age of the new group is 700 - 20 = 680 years, because the new member is 20 years younger than the former member. For the average age of the new group, divide 680 by 20 to get 34.

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If I have an average of unknown numbers and a new number, how do I calculate the new average? e.g. average of Z numbers is 52 and new number is 55, new average is (52 x Z + 55) / (Z + 1) = ?

Donagan

Top Answerer

That formula is correct. Assuming you know Z, that formula will let you calculate the new average.

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If 5 girls have an average of 10p, what is the total?

Donagan

Top Answerer

The total is 5 x 10p, or 50p.

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What are the 5 numbers with the median of 32 and the mean of 54?

Will Massey

Community Answer

30,31,32,33,144. You have to satisfy the middle number is 32 and other four (two either side) sum to 238. Any 4 numbers that do this will work.

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In a group of 60 numbers, the average of the first 35 numbers is 18, that of next 15 numbers is 10, and remaining is 30. What is average of entire group?

Will Massey

Community Answer

18. (35*18+15*10+10*30)/60=18 you can just assume that the numbers with average of 18 are all 18.

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100 people lived for 15 years, 20 lived for 18 years and 2 lived for 40 years each. What is the average life expectancy here?

Donagan

Top Answerer

100 x 15 = 1,500. 20 x 18 = 360. 2 x 40 = 80. Add 1,500 + 360 + 80 = 1,940 (the total number of years lived). Divide 1,940 by 122 (the total number of people studied). 1,940 ÷ 122 = 15.9 years (the average life expectancy).

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What 4 numbers make the average of 11?

Donagan

Top Answerer

Multiply 11 by 4. That's 44. Now pick any four numbers that add up to 44. To make it easier, pick any two numbers that add up to 22 and two more that also add up to 22.

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I have 16 loads, weighed 4. How do I get an average?

Donagan

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You can find only the average of the four weighed loads: add them together and divide by 4.

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How do I average wages that are one number for most of a year, but another number for part of it?

Donagan

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Calculate the total pay for the year, then divide that by the number of pay checks.

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What if they are negative numbers?

Donagan

Top Answerer

In finding an average of some numbers, it makes no difference if some or all of them are negative. You still add them together. Adding a negative number is the same as subtracting a (positive) number. So you add them all together, and divide by the number of numbers.

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Summary of 42 responses shows 37 people gave a 4, 3 people gave 3, 2 people gave 2 and 0 people gave 0. What is the average?

Donagan

Top Answerer

[(37)(4) + (3)(3) + (2)(2) + (0)(0)] / 42 = [148 + 9 + 4 + 0] / 42 = 161 / 42 = 3.83, the average.

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How do I find the average of 20 numbers without adding all the numbers together?

Donagan

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You could make an estimate, but if you want a precise average, you have no choice but to add the numbers together and divide the sum by 20.

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How do I find the average of a group of numbers if one number is missing?

Donagan

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There is no way to do it. You could calculate the average without the missing number and make it known that one number was missing from the calculation.

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Question

What is the average of 9.8, 9.5 and 9.7?

I_l1ke_gam3s

Community Answer

Add these three numbers and divide by 3: 9.8 + 9.5 + 9.7 = 29. The average is 29/3, which is 9 2/3 or 9.67.

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What is the average of 2, 4, 6, 8 and 10?

I_l1ke_gam3s

Community Answer

Add these up and divide by 5: 2 + 4 + 6 + 8 + 10 = 30. 30/5 = 6. The average (mean) of this data set is 6.

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What is the average of 600, 1000, 800, 500 and 700?

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(600 + 1000 + 800 + 500 + 700) / 5 = 36,000 / 5 = 720.

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