Phone plan A charges $1.25 for the first minute and $0.15

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BTGmoderatorDC: Moderator; Posts: 7187; Joined: Thu Sep 07, 2017 4:43 pm; Followed by:23 members

Phone plan A charges $1.25 for the first minute and $0.15

by BTGmoderatorDC » Tue Apr 23, 2019 8:20 pm

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Phone plan A charges $1.25 for the first minute and $0.15 for every minute thereafter. Phone plan B charges a $0.90 connection fee and $0.20 per minute. Which of the following equations could be used to find the length, in minutes, of a phone call that costs the same under either plan?

(A) 1.25 + 0.15x = 0.90x + 0.20
(B) 1.25 + 0.15x = 0.90 + 0.20x
(C) 1.25 + 0.15(x - 1) = 0.90 + 0.20x
(D) 1.25 + 0.15(x - 1) = 0.90 + 0.20(x - 1)
(E) 1.25 + 0.15x + 0.90x + 0.20 = x

OA C

Source: Manhattan Prep

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Source: Beat The GMAT — Problem Solving | Tue Apr 23, 2019 8:20 pm

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by Brent@GMATPrepNow » Wed Apr 24, 2019 4:51 am

BTGmoderatorDC wrote:Phone plan A charges $1.25 for the first minute and $0.15 for every minute thereafter. Phone plan B charges a $0.90 connection fee and $0.20 per minute. Which of the following equations could be used to find the length, in minutes, of a phone call that costs the same under either plan?

(A) 1.25 + 0.15x = 0.90x + 0.20
(B) 1.25 + 0.15x = 0.90 + 0.20x
(C) 1.25 + 0.15(x - 1) = 0.90 + 0.20x
(D) 1.25 + 0.15(x - 1) = 0.90 + 0.20(x - 1)
(E) 1.25 + 0.15x + 0.90x + 0.20 = x

OA C

Source: Manhattan Prep

Phone plan A charges $1.25 for the first minute and $0.15 for every minute thereafter.
Let x = total duration of phone call (in minutes)
So, the cost of an x-minute call = $1.25 + ($0.15)(x - 1)

ASIDE: I created the expression ($0.15)(x - 1) because we pay $1.25 for the FIRST minute. So, if x = the TOTAL call time, then x-1 = the time spent AFTER the first minute)

Phone plan B charges a $0.90 connection fee and $0.20 per minute.
Let x = total duration of phone call (in minutes)
So, the cost of an x-minute call = $0.90 + ($0.20)(x)

Which of the following equations could be used to find the length, in minutes, of a phone call that costs the same under either plan?
We need: $1.25 + ($0.15)(x - 1) = $0.90 + ($0.20)(x)

Answer: C

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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by Scott@TargetTestPrep » Thu Apr 25, 2019 5:50 pm

BTGmoderatorDC wrote:Phone plan A charges $1.25 for the first minute and $0.15 for every minute thereafter. Phone plan B charges a $0.90 connection fee and $0.20 per minute. Which of the following equations could be used to find the length, in minutes, of a phone call that costs the same under either plan?

(A) 1.25 + 0.15x = 0.90x + 0.20
(B) 1.25 + 0.15x = 0.90 + 0.20x
(C) 1.25 + 0.15(x - 1) = 0.90 + 0.20x
(D) 1.25 + 0.15(x - 1) = 0.90 + 0.20(x - 1)
(E) 1.25 + 0.15x + 0.90x + 0.20 = x

OA C

Source: Manhattan Prep

We can create the equation in which x = the number of minutes that equates the charges of the two plans. Plan A charges $1.25 for the first minute and $0.15 for the remaining (x - 1) minutes. Plan B charges a $0.90 fee and $0.20 for all x minutes of the call. Thus, the equation that equates the charges for the two plans is:

1.25 + 0.15(x - 1) = 0.9 + 0.2x

Answer: C

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