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

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

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

Steps: 7

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.