Question

1. A motorcycle dealer has 9 adventure bikes for sale. She wants to mark down two of these for a special sale. How many different pairs of these nine adventure bikes are possible, if she randomly selects two to feature in the sale?

2. Suppose Babies' birth weights follow normal distribution with a mean of 120 ounces and a standard deviation of 20 ounces. Approximately what proportion of babies will weigh between 5 and 7.5 pounds at birth?

3. The speeds at which cars travel through a certain section of I-70 are known to be positively skewed with a mean of 72 miles per hour with a standard deviation of 4 mph. what can be said about the approximate proportion of cars traveling in excess of 85 mph?

If you could answer any of these that would be great. Thanks!

Answer 1

#1: Since order does not matter, use combination. Number of different pairs of these nine adventure bikes are:

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#2: We know, .

Given . Proportion of babies will weigh between 5 and 7.5 pounds at birth (between 80 and 120 ounces) is:

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#3: Since population is skewed, there is no way to calculate proportion of cars traveling in excess of 85 mph.