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IP2U15 HOT Q3

IP2U15 HOT Q3

Secondary 4

The number of minutes taken by four boys to complete a question is \(x - y\), \(8\), \(10\) and \(x + y\). The mean time taken is \(9\) minutes.

  1. Show that \(x = 9\).
  2. Given that the standard deviation is \(5\) minutes, find the value of \(y\).
  3. Four girls answered the same question and the mean time taken is also \(9\) minutes but the standard deviation is \(2\) minutes. Compare and comment on these two sets of data.

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Answer:(a) \(x=9\) (shown) (b) \(y=\pm7\) (c) Both means are \(9\) minutes; the girls are more consistent because their standard deviation is \(2\) minutes versus \(5\) minutes for the boys

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