GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
If 1/2 of the air in a tank is removed with each stroke of a vacuum pu
[#permalink]
13 Jun 2022, 01:00
13 Jun 2022, 01:00
Expert Reply
2
Bookmarks
00:00
Question Stats:
48% (01:19) correct
52% (01:16) wrong based on 25 sessions
Hide Show timer Statistics
If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes ?
A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16
A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16
Part of the project: GRE QCQ & PS 3 Questions Every One DAILY Challenge - (2022)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GRE Math Essentials for a TOP Quant Score - Q170!!! (2021)
GRE Geometry Formulas for a Q170
GRE - Math Book
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If 1/2 of the air in a tank is removed with each stroke of a vacuum pu
[#permalink]
13 Jun 2022, 06:08
13 Jun 2022, 06:08
1
Carcass wrote:
If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes ?
A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16
A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16
Strategy: Since the question is asking us to find a certain fraction (and not the actual volume of air that has been removed), let's assign a nice, easy-to-work-with value for the original volume of air in the tank.
Since we keep halving the volume of air, let's say there are 64 liters of are in the tank at the beginning, and will keep track of the volume after each stroke.
Initial volume: 64 liters
Volume of air remaining after 1 stroke: 32 liters
Volume of air remaining after 2 strokes: 16 liters
Volume of air remaining after 3 strokes: 8 liters
Volume of air remaining after 4 strokes: 4 liters
If 4 liters of air remain in the tank, then the volume of air that was removed = 64 - 4 = 60 liters
So, the fraction of the original amount of air has been removed after 4 strokes = 60/64 = 30/32 = 15/16
Answer: A
If 1/2 of the air in a tank is removed with each stroke of a vacuum pu
[#permalink]
11 Dec 2023, 13:06
11 Dec 2023, 13:06
I dont understand Brent... How do we keep assigning values like this? can we not solve this way. 1 - 1/2 = 1/2.. And since its done 4x... we then do this... 1/2*1/2*1/2*1/2 = 1/16?
Also when presented with word fraction problems... when do we assign values and when do we not?
Also when presented with word fraction problems... when do we assign values and when do we not?
