The average of two numbers is 30. If one number is 20, what is the other number?

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Question: The average of two numbers is 30. If one number is 20, what is the other number?

Options:

Correct Answer: 40

Solution:

Mean = (20 + x) / 2 = 30.\\n\\n20 + x = 60\\n\\nx = 60 - 20 = 40.

The average of two numbers is 30. If one number is 20, what is the other number?

The average of two numbers is 30. If one number is 20, what is the other number?

Step 1: Understand that the average (mean) of two numbers is calculated by adding the two numbers together and then dividing by 2.
Step 2: Write down the formula for the average: (first number + second number) / 2 = average.
Step 3: Substitute the known values into the formula. We know one number is 20 and the average is 30, so we write: (20 + x) / 2 = 30.
Step 4: To eliminate the division by 2, multiply both sides of the equation by 2. This gives us: 20 + x = 60.
Step 5: Now, solve for x by subtracting 20 from both sides of the equation: x = 60 - 20.
Step 6: Calculate the result: x = 40. This means the other number is 40.

Average Calculation – Understanding how to calculate the average (mean) of two numbers and manipulate the equation to find an unknown value.
Algebraic Manipulation – Applying basic algebra to isolate the variable and solve for it.