Connecting Averages Xian Yi

The question below is asking for the fourth number that makes the mean 7. We know that the method of finding the mean is adding up all the numbers and then dividing them by however many numbers are there, e.g. 1,2,3,6. 1+2+3+6= 12, and 12 divided by 4 is 3. Therefore, the mean is 3. In this case, we don’t know what the fourth number is. But we do know that the number all four numbers sum up to is the mean multiplied by 4, which is 7 times four, which gives us 28. This means that since the sum of all the numbers added together is 28, if we add up all the numbers that we already have, it gives us 4. So 28-4=24. Therefore, the last number must be 24. To double-check our work, we add together 2,2,0 and 24, which gives us 28. 28 then divided by 4 is 7. So, our answer is 24!