[求助] PP数学问题~~大牛请进

i92

1.

1.

A vending machine is designed to dispense 8 ounces of coffee into a cup.  After a test that recorded the number of ounces of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in ounces, were selected from the data.  If the 1,000 recorded amounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounce, how many of the 12 listed amounts are within 1.5 standard deviations of the mean?

(A) Four  (B) Six  (C) Nine  (D) Ten  (E) Eleven

answer:E

2.

Two water pumps, working simultaneously at their respective constant rates, took exactly 4 hours to fill a certain swimming pool.  If the constant rate of one pump was 1.5 times the constant rate of the other, how many hours would it have taken the faster pump to fill the pool if it had worked alone at its constant rate?

(A) 5  (B)  (C)  (D) 6  (E) 

answer:E (PP上没解答)

3.If a certain wheel turns at a constant rate of x revolutions per minute, how many revolutions will the wheel make in k seconds?(A) 60kx  (B) kx (C)  (D)  (E) 

answer:E (PP上没解答)

4.

S represents the sum of the weights of n fish in pounds.  Which of the following represents the average (arithmetic mean) of the n weights in ounces? (1 pound = 16 ounces)

(A) 16nS (B)  (C)  (D)  (E) 

answer:B (PP上没解答)

 

Two water pumps, working simultaneously at their respective constant rates, took exactly 4 hours to fill a certain swimming pool.  If the constant rate of one pump was 1.5 times the constant rate of the other, how many hours would it have taken the faster pump to fill the pool if it had worked alone at its constant rate?

(A) 5  (B)  (C)  (D) 6  (E) 

answer:E (PP上没解答)

3.If a certain wheel turns at a constant rate of x revolutions per minute, how many revolutions will the wheel make in k seconds?(A) 60kx  (B) kx (C)  (D)  (E) 

answer:E (PP上没解答)

4.

S represents the sum of the weights of n fish in pounds.  Which of the following represents the average (arithmetic mean) of the n weights in ounces? (1 pound = 16 ounces)

(A) 16nS (B)  (C)  (D)  (E) 

answer:B (PP上没解答)

 

4.

S represents the sum of the weights of n fish in pounds.  Which of the following represents the average (arithmetic mean) of the n weights in ounces? (1 pound = 16 ounces)

(A) 16nS (B)  (C)  (D)  (E) 

answer:B (PP上没解答)

 

[此贴子已经被作者于2008-2-22 21:50:00编辑过]

heslaw

For 1, 1.5 std dev is 0.3*1.5 around the mean 8.1

2. rate 1= x, rate two= 1.5x, then get x from the 4 hrs given, then use 1/(1.5x), get ans

3.in 1 sec, rev= x/60, so k secs, (kx)/60

4.(16s)/n    

i92

anothermonk

第一题的解答没有看懂的说。。

arguu

1.是不是少了什么条件或者表什么的？

2. 20/3

3,4和2楼一样

heslaw

第一题楼主要仔细看看题目给了什么数

flyinggrape

第一题确实少了条件。据多方考证，Prep资料里录入这个题的时候没有把那12个数字写出来。所以有了那12个samples的具体值之后就很好做了 你看题目描述有个“ the 12 listed amounts”