The arithmetic mean of two numbers is 21.4. Find the second number if the first number is 8.4

Let the second number be x. Knowing the arithmetic mean of two numbers and the first number, we can make an equation and solve it:

(8.4 + x) / 2 = 21.4;

8.4 + x = 21.4 * 2;

8.4 + x = 42.8;

x = 42.8 – 8.4;

x = 34.4.

If x = 34.4, then the second number is 34.4.

Answer: 34.4.

Examination:

(8.4 + 34.4) / 2 = 21.4;

42.8 / 2 = 21.4;

21.4 = 21.4.