Multiple choice

When 10 is subtracted from all the observations, the mean is reduced to 60% of its value. If 5 is added to all the observations, then the mean will be

  1. 25

  2. 30

  3. 60

  4. 65
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let mean be M. (M-10) = 0.6M => 0.4M = 10 => M = 25. If 5 is added to all, new mean = M + 5 = 25 + 5 = 30.

AI explanation

Let the original mean be M; subtracting 10 makes the new mean 0.6M, so M minus 10 equals 0.6M, which means 0.4M equals 10 and M is 25. When 5 is added to all observations, the new mean becomes M plus 5, so 25 plus 5 gives a new mean of 30.

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