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Question

The average of five numbers is 15. If each number is divided by 3, what will be the average of the new set of numbers?

The correct answer is
5

The problem requires determining the new average when each number of a set is divided by 3, given that the original average is 15.

  1. The average of a set of numbers is calculated as the sum of the numbers divided by the total count of numbers. 
    Let us denote the sum of the original five numbers as \(S\). Given that the average is 15, we have: \(\frac{S}{5} = 15\).
  2. From the equation in step 1, we can find \(S\):

\(S = 15 \times 5 = 75\)

  1. When each number is divided by 3, the sum of the new numbers becomes \(\frac{S}{3}\)
    Thus, the sum of the numbers becomes:

\(\frac{75}{3} = 25\)

  1. Now, calculate the average of the new set of numbers. Since the total count remains the same (five numbers), the new average will be:

\(\frac{25}{5} = 5\)

Thus, the average of the new set of numbers when each number is divided by 3 becomes 5.

The correct answer is 5, which matches the provided correct answer.

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Important Questions from Average

  1. Average of 40 numbers is 71, if the number 100 replaced by 140, then average is increased by

  2. The captain of a football team of 11 members is 28 years old and the goalkeeper is 4 years older than him. If the ages of these two are removed, then the average age of the remaining players is two years less than the average age of the whole team. What is the average age of the team?

  3. There are two Classes A and B having 25 and 30 students respectively. In Class-A the highest score is 21 and lowest score is 17. In Class-B the highest score is 30 and lowest score is 22. Four students are shifted from Class-A to Class-B.

    Consider the following statements:

    1. The average score of Class-B will definitely decrease.

    2. The average score of Class-A will definitely increase.

    Which of the above statements is/are correct?

  4. The average weight of A, B, Cis 40 kg, the average weight of B, D, Eis 42 kg and the weight of Fis equal to that of B. What is the average weight of A, B, C, D, Eand F?

  5. A cow costs more than 4 goats but less than 5 goats. If a goat costs between Rs. 600 and Rs. 800, which of the following is a most valid conclusion?

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