求助,PREP

126.   12631-!-item-!-187;#058&009380

9.4  9.9  9.9  9.9  10.0  10.2  10.2  10.5

The mean and the standard deviation of the 8 numbers shown are 10.0 and 0.3, respectively.  What percent of the 8 numbers are within 1 standard deviation of the mean?

(A) 90%

(B) 85%

(C) 80%

(D) 75%

(E) 70%

答案是D

127.   12731-!-item-!-187;#058&009562

In May, Xiang sold 15 used cars.  For these 15 cars, the range of the selling prices was $15,000 and the lowest selling price was $4,500.  In June, Xiang sold 10 used cars.  For these 10 cars, the range of the selling prices was $16,500 and the lowest selling price was $6,100.  What was the range of the selling prices of the 25 used cars sold by Xiang in May and June?

(A) $15,600

(B) $15,750

(C) $16,820

(D) $18,100

(E) $19,200

答案是D