help hard QR questions

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11. Which of the following procedures is
always equivalent to adding 5 given
numbers and then dividing the sum by
5 ?
I. Multiplying the 5 numbers and then
finding the 5th root of the product.
II. Adding the 5 numbers, doubling the
sum, and then moving the decimal
point one place to the left.
III. Ordering the 5 numbers
numerically and then selecting the
middle number.
(A) None
(B) I only
(C) II only
(D) III only
(E) I and III

On a certain road, 10 percent of the
motorists exceed the posted speed
limit and receive speeding tickets, but
20 percent of the motorists who
exceed the posted speed limit do not
receive speeding tickets. What percent
of the motorists on that road exceed
the posted speed limit ?

answer: 12.5%

If a 10 percent deposit that has been
paid toward the purchase of a certain
product is $110, how much more
remains to he paid?
(A) $880
(B) $900
(C) $1,000
(D) $1,100
(E) $1,210

asnwer: B

 

[Clubby]

The answer to the third one is $990. Looks like an error. Where did you get this from?

The first one I think is none.

The second one was ridiculously easy.

 

[BenignDMD]

Third problem:

(.1)(x)=110

x=1100

1100-110 = 990.

Are you sure B is not 990?

 

[BenignDMD]

second problem is easy. you just need to setup a ratio:

t = total # of drivers on road

e = # of drivers who exceed limit

(.1)(t) = total # of drivers on road who exceed and get ticket

(.2)(e) = # of drivers who exceed limit but do not get a ticket

therefore (.8)(e) = # of drivers who exceed limit and get ticket.

(.1)(t) = (.8)(e)

.1/.8 = e/t

so 12.5% of drivers exceed the limit

 

[BenignDMD]

1st problem is C....only II works

using variables:

(A+B+C+D+E)/5 is our original procedure

Choice II:

(A+B+C+D+E)

then double the sum:

(A+B+C+D+E)(2)

then move the decimal point over to the left (which just means divide by 10):

(A+B+C+D+E)(2)
----------------
(10)

2/10 is 1/5 so your expression is still"

(A+B+C+D+E)/5

 

[airsimon]

saaa

 

[BenignDMD]

saaa

Huh??

 

[desiballas]

yea benigndmd, i got $990 too