If the average of three numbers is 15 and the first two numbers are 10 and 20, w

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Question: If the average of three numbers is 15 and the first two numbers are 10 and 20, what is the third number?

Options:

Correct Answer: 25

Solution:

Total of three numbers = 3 * 15 = 45. Sum of first two numbers = 10 + 20 = 30. Third number = 45 - 30 = 15.

If the average of three numbers is 15 and the first two numbers are 10 and 20, what is the third number?

If the average of three numbers is 15 and the first two numbers are 10 and 20, what is the third number?

Correct Answer: 15

Step 1: Understand that the average of three numbers is given as 15.
Step 2: Recall that the average is calculated by adding all the numbers together and then dividing by the number of numbers.
Step 3: Since there are three numbers, multiply the average (15) by 3 to find the total of the three numbers: 3 * 15 = 45.
Step 4: You are given the first two numbers, which are 10 and 20.
Step 5: Add the first two numbers together: 10 + 20 = 30.
Step 6: To find the third number, subtract the sum of the first two numbers (30) from the total of the three numbers (45): 45 - 30 = 15.
Step 7: Therefore, the third number is 15.

Average Calculation – Understanding how to calculate the average of a set of numbers and how to derive individual values from it.
Basic Arithmetic – Applying addition and subtraction to find the missing number based on the average.