Q&A for How to Calculate Weighted Average

If you have the numbers 3, 5, and 10, to take a normal average, it would be 3+5+10, divided by the total number of data points—in this case 3. For a weighted average, you'd multiply each number by its weight first. For instance, if the first number is twice as important, it would have a weight of 2, while the others would have a weight of 1. In that case, it would be (3x2)+(5x1)+(10x1). Then, divide that by 3.

In this case, your weights add up to 1.75, or 175%. To find your score, first add up the individual scores multiplied by their weights: 50(.5) + 70(.5) + 100(.25) + 100(.25) + 7(.25) = 111.75. Then, divide the result by the total weight: 111.75/1.75 = 63.86. This means your grade average in the class is 63.86, which you can round up to 64.

That depends on whether the total weights of the scores add up to 100%. If so, then you would multiply each score (x) by its percentage of the total grade (w) and add them all up. So the formula would look like x1(w1) + x2(w2), etc. If it's possible to achieve a total score that is greater or less than 100%, you'd have to divide the sum of all scores(weights) by the total possible weight.

Multiply 10 by 80 (800). Multiply 15 by 60 (900). Add 800 and 900 (1700). Divide 1700 by 25 (10 + 15). That equals 68, the class average.

You must know the relative "weight" (or importance) of those two numbers before you can calculate their average. For example, if those two numbers were test scores, you would have to know how much importance ("weight") the teacher has assigned to each test. You then multiply the weight (usually given as a percentage) of each test by its score, add the two "weighted" scores together, and divide by the number of scores (in this case, two).

Multiply $15,000 by 5 (months). To that product add the product of $13,000 and 2 (months). To that sum add the product of $11,500 and 3 (months). To that sum add the product of $$15,500 and 2 (months) (assuming you're considering a full year through the end of December). Then divide this final sum by 12 to find the monthly average for the year. Thus: [($15,000 x 5) + ($13,000 x 2) + ($11,500 x 3) + ($15,500 x 2)] ÷ 12 = ($75,000 + $26,000 + $34,500 + $31,000) ÷ 12 = $166,500 ÷ 12 = $13,875 (the average balance during the year).

You'd expect the answer to be a little less than 38 seconds, since the 3 instantaneous answers hould bring the average down. Here is the equation: (79 x 38) + (3 x 0) = 3002. Divide by 82 to get the weighted average: 3002/82 = 36.1.

Calculate the volume of the water, then multiply by the density of water (one gram per milliliter or cubic centimeter at normal pressure and room temperature).

You would algebraically add the negative score(s) to the positive score(s), and divide by the total number of scores (both positive and negative). Algebraically adding negative numbers means simply subtracting. If the scores are weighted, you would multiply each score by its weighting (expressed as a percentage) before adding or subtracting the score.

Just use a BMI calculator, which can be found online.

The values would be provided for you, or in some cases you might have to measure them for yourself.

Assuming each response is given equal weight (as is the case in most surveys), there would be no weighted average in this case.

Multiply the value by the number of times it occurs in a given data set. Do the same for every different value that occurs.

It depends on the grades and weighting given to the other assignments.

There's really no such thing as a weighted average when it comes to money. You would simply have various quantities of bills and/or coins of different denominations, while a weighted average wouldn't really make much sense. (You'd be saying after counting all the money that the average bill or coin was worth, say, $3.47).

Divide the total number of games played by the number of games won for a good estimate of the probability. If you want to know how accurate this is, then you need to use statistics.

This problem is solvable for two weights, but no more. You should set up the usual weighted average equation like (aA + bB)/(a+b) = M, where a is the weight of A and b is the weight of B, and the weighted average M is between A and B. Since there are two unknowns in one equation, you can't solve it for weights a or b, but you can solve it for the ratio a/b. Algebraically manipulate the equation until it looks like a(A-M) + b(B-M) = 0, and from there, a(A-M) = b(B-M) and a/b = (M-B)/(A-M).

The simple formula to calculate weighted average is: =SUMPRODUCT(Column 1,Column 2) /SUM(Column 2). Dividing the sum product by sum of Column 1 entries will give weighted average for Column 2.

You can't answer this without knowing how many "other" students there were.