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DS - Equations

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DS - Equations

by phoenix9801 » Sat Jul 10, 2010 9:52 pm
Hi, can someone please help to explain by step-by-step instructions (in detail) in the most simplest way and clear to understand. Would Greatly appreciate it.

1-

The Charge for a telephone call between City R and City S is $0.42 for each of the first 3 minutes and $0.18 for each additional minutes. A certain call between these two cities lasted for x minutes, where x is an integer. How many minutes long was the call?

(1) the charge for the first 3 minutes of the call was $0.36 less than the charge for the reminder of the call.

(2) The total charge for the call was $2.88





2-

For all intergers n, the function f is defined by f(n)=a^n, where a is constant. What is the value of f(1)?

(1) f(2) = 100

(2) f(3) = - 1,000
Last edited by phoenix9801 on Mon Jul 12, 2010 1:52 pm, edited 1 time in total.
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by gmatmachoman » Sat Jul 10, 2010 10:51 pm
2-

For all intergers n, the function f is defined by f(n)=a^n, where a is constant. What is the value of f(1)?

(1) f(2) = 100

(2) f(3) = - 1,000


Pick B

f(n)=a^n

st 1 :


n = 2
a = ?

(1) f(2) = 100

= a ^n
=10 ^2 or (-10) ^2

Insufficient as a can be 10 or -10

st 2:

Upon calculation a = -10 only

sufficient

Pick B
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by diebeatsthegmat » Sun Jul 11, 2010 1:49 am
phoenix9801 wrote:Hi, can someone please help to explain by step-by-step instructions (in detail) in the most simplest way and clear to understand. Would Greatly appreciate it.

1-

The Charge for a telephone call between City R and City S is $0.42 for each of the first 3 minutes and $0.18 for each additional minutes. A certain call between these two cities lasted for x minutes, where x is an integer. How many minutes long was the call?

(1) the charge for the first 3 minutes of the call was $0.36 less than the charge for the reminder of the call.

(2) The total charge for the call was $2.88





2-

For all intergers n, the function f is defined by f(n)=a^n, where a is constant. What is the value of f(1)?

(1) f(2) = 100

(2) f(3) = - 1,000
1-

The Charge for a telephone call between City R and City S is $0.42 for each of the first 3 minutes and $0.18 for each additional minutes. A certain call between these two cities lasted for x minutes, where x is an integer. How many minutes long was the call?

(1) the charge for the first 3 minutes of the call was $0.36 less than the charge for the reminder of the call.
3*0.42=0.18*y-0.36 ( y is the number of minute for the remainder call) we can find the value of y and then y+3 ( the first minutes called) sufficient

(2) The total charge for the call was $2.88
3*0.42+0.18*z=2.88 we also can find z and z+3= the number of minutes the call last. sufficient
OA is D




2-

For all intergers n, the function f is defined by f(n)=a^n, where a is constant. What is the value of f(1)?

(1) f(2) = 100
f(2)=10^2 so a =10 or a=-10 insufficient
(2) f(3) = - 1,000
f(3)=(-10)^3 thus a=-10 sufficient
OA is B
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