Question

The average of four numbers is 80.If first three numbers are 80, 90 and 100, find the fourth number.​

Answer 1

Answer:

The average of four numbers is 80.If first three numbers are 80, 90 and 100, find the fourth number.

Answer 2

The fourth number is 50.

Given - Average and three numbers

Find - Fourth number

Solution - Let the fourth number be x. Now, as we know, the formula of average is -

Average = sum of all observations/total number of observations

We will be adding up the three numbers with x and keep the values in formula.

Sum = 80 + 90 + 100 + x

Sum = 270 + x

80 = (270 + x)/4

270 + x = 80*4

Performing multiplication on Right Hand Side

270 + x = 320

x = 320 - 270

Performing subtraction on Right Hand Side

x = 50

Hence, the fourth number is 50.

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