BhargaviVishnu wrote:

Can you please elaborate the answer

You need to map the problem onto the graph such that the mean and standard deviations account for the approprite points.

Given thet mean travel time is 35 mins and one standard deviation is 35 + 5 mins. or 35 - 5 mins.

So we mark the corresponding points onto the graph as shown below. Now the question asks for the percentage of time Ian was travelling less than 40 mins.

Clearly we are being aasked the value of the area shaded in blue. So the answer is E.

Attachments

Inkeddistribution_LI.jpg [ 831.07 KiB | Viewed 562 times ]

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Sandy

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