# The arithmetic mean of three numbers is 8. Find the third number if the first is 12.4 and the second is 8.2.

December 27, 2020 | education

| Let the third number be x. Knowing the first number – 12.4, the second number – 8.2, the arithmetic mean of three numbers – 8, we can draw up an equation and solve it.

Let’s see what happens:

(12.4 + 8.2 + x) / 3 = 8;

(20.6 + x) / 3 = 8, we solve by the method of multiplication crosswise:

20.6 + x = 8 * 3;

20.6 + x = 24, x is found as an unknown term, that is:

x = 24 – 20.6;

x = 3.4.

If x = 3.4, then the third number is 3.4.

Answer: 3.4.

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