Passage

SECTION - A (MATHEMATICS)

If the mean of first 10 numbers is 15 and mean of next 10 numbers is double the mean of consecutive next 10 numbers. If last two numbers are 10 and 5 and total mean of all the numbers is 15. Find the mean of last 12 observations.

The mean of the first 10 numbers is 15, so their sum is 150. Let the mean of the next 10 numbers be 2x and the mean of the following 10 numbers be x, making their combined sum 30x, and since the last two numbers are 10 and 5, the sum of all 32 numbers is 150 plus 30x plus 15, which equals 165 plus 30x. The total mean of all 32 numbers is 15, making the overall sum 32 times 15, which is 480, so solving 165 plus 30x equals 480 gives 30x equals 315, meaning the sum of the last 12 numbers is 30x plus 15, or 330. The mean of the last 12 observations is their sum divided by 12, so 330 divided by 12 equals 12.

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