Multiple choice

The average of 6 numbers is 30. If the average of the first four numbers is 25 and that of the last three numbers is 35, find the fourth number.

  1. 25

  2. 30

  3. 35

  4. 40
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A Correct answer
Explanation

Total sum of 6 numbers = 6 * 30 = 180. Sum of first 4 = 4 * 25 = 100. Sum of last 3 = 3 * 35 = 105. The fourth number is (Sum of first 4 + Sum of last 3) - Total sum = (100 + 105) - 180 = 205 - 180 = 25.

AI explanation

The sum of all 6 numbers is 6 times 30, which equals 180. The sum of the first four numbers is 4 times 25, resulting in 100, and the sum of the last three numbers is 3 times 35, resulting in 105. If you add the sum of the first four numbers and the sum of the last three numbers, you get 100 plus 105, which equals 205, but this sum counts the fourth number twice. To find the fourth number, subtract the total sum of all six numbers from this combined sum, giving 205 minus 180, which results in 25.

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