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A satellite is composed of 30 modular units, each of which

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A satellite is composed of 30 modular units, each of which [#permalink]  23 Sep 2016, 14:16
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29% (02:02) correct 70% (02:15) wrong based on 55 sessions
A satellite is composed of 30 modular units, each of which is equipped with a set of sensors, some of which have been upgraded. Each unit contains the same number of non-upgraded sensors. If the number of non-upgraded sensors on one unit is 1/5 the total number of upgraded sensors on the entire satellite, what fraction of the sensors on the satellite have been upgraded?

A)5/6
B)1/5
C)1/6
D)1/7
E)1/2
[Reveal] Spoiler: OA

_________________

Brent Hanneson – Creator of greenlighttestprep.com

GRE Instructor
Joined: 10 Apr 2015
Posts: 2601
Followers: 96

Kudos [?]: 2800 [3] , given: 41

Re: A satellite is composed of 30 modular units, each of which [#permalink]  23 Sep 2016, 14:17
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Expert's post
GreenlightTestPrep wrote:
A satellite is composed of 30 modular units, each of which is equipped with a set of sensors, some of which have been upgraded. Each unit contains the same number of non-upgraded sensors. If the number of non-upgraded sensors on one unit is 1/5 the total number of upgraded sensors on the entire satellite, what fraction of the sensors on the satellite have been upgraded?

A)5/6
B)1/5
C)1/6
D)1/7
E)1/2

Since we're asked to find a certain FRACTION, we can plug in some nice values that meet the given conditions.

Let's say that there's a TOTAL of 5 upgraded sensors on the entire satellite

the number of non-upgraded sensors on one modular unit is 1/5 the TOTAL number of upgraded sensors on the entire satellite
So, the number of non-upgraded sensors on EACH modular unit = (1/5)(5) = 1.

Since there are 30 modular units altogether, the TOTAL number of non-upgraded sensors = (30)(1) = 30.

So, the TOTAL number of sensors = (number of non-upgrades) + (number of upgraded)
= 30 + 5
= 35

What fraction of the sensors on the satellite have been upgraded?
= 5/35
= 1/7

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

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Re: A satellite is composed of 30 modular units, each of which [#permalink]  03 Jul 2018, 06:27
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Let, non-upgradable sensor per module (or 1 module) = x
Total no. of sensor = T
Total no. of upgraded sensors = y = T - 30x
Logic line: x = (1/5)*y So, y = 5x
or, x = (1/5)*(T - 30x)
solving, T = 35x
so, y/T = 5x/35x = 1/7
GRE Instructor
Joined: 10 Apr 2015
Posts: 2601
Followers: 96

Kudos [?]: 2800 [2] , given: 41

Re: A satellite is composed of 30 modular units, each of which [#permalink]  11 Jul 2019, 06:42
2
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Expert's post
GreenlightTestPrep wrote:
A satellite is composed of 30 modular units, each of which is equipped with a set of sensors, some of which have been upgraded. Each unit contains the same number of non-upgraded sensors. If the number of non-upgraded sensors on one unit is 1/5 the total number of upgraded sensors on the entire satellite, what fraction of the sensors on the satellite have been upgraded?

A)5/6
B)1/5
C)1/6
D)1/7
E)1/2

Let's say that there's a TOTAL of x upgraded sensors on the entire satellite

the number of non-upgraded sensors on one modular unit is 1/5 the TOTAL number of upgraded sensors on the entire satellite
So, the number of non-upgraded sensors on EACH modular unit = (1/5)(x) = x/5.

Since there are 30 modular units altogether, the TOTAL number of non-upgraded sensors = (30)(x/5) = 30x/5 = 6x.

So, the TOTAL number of sensors = (number of non-upgrades) + (number of upgraded)
= 6x + x
= 7x

What fraction of the sensors on the satellite have been upgraded?
= x/7x
= 1/7

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

Intern
Joined: 23 Jul 2019
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Kudos [?]: 1 [0], given: 13

Re: A satellite is composed of 30 modular units, each of which [#permalink]  06 Aug 2019, 23:05
Let no. of non-upgraded sensors per module be x
Total non-upgraded sensors = 30x (since each module has same no. of non-upgraded sensors)

Let total upgraded sensors be T
From given condition: x=1/5*T
or, T= 5x

Now,

Total no. of sensors = 5x+30x = 35x

so fraction of upgraded = 5x/35x = 1/7

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Joined: 01 Aug 2019
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Re: A satellite is composed of 30 modular units, each of which [#permalink]  07 Aug 2019, 00:24
Wow, this is the topic! How much I know, but this is the first time I've ever met! Wow!
GRE Instructor
Joined: 10 Apr 2015
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Kudos [?]: 2800 [1] , given: 41

Re: A satellite is composed of 30 modular units, each of which [#permalink]  28 Aug 2019, 08:45
1
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Expert's post
GreenlightTestPrep wrote:
A satellite is composed of 30 modular units, each of which is equipped with a set of sensors, some of which have been upgraded. Each unit contains the same number of non-upgraded sensors. If the number of non-upgraded sensors on one unit is 1/5 the total number of upgraded sensors on the entire satellite, what fraction of the sensors on the satellite have been upgraded?

A)5/6
B)1/5
C)1/6
D)1/7
E)1/2

A student asked me to add some graphics to my solution, so......

A satellite is composed of 30 modular units, each of which is equipped with a set of sensors, some of which have been upgraded. Each unit contains the same number of non-upgraded sensors.
So, here's a sketch of 30 modular units.

The circles inside each unit represent sensors. The circles with black centers represent NON-upgraded sensors, and the empty red circles represent upgraded sensors.
For my sketch, I placed ONE NON-upgraded sensor in each of the 30 modular units (since we're told that each unit contains the same number of non-upgraded sensors)

The number of non-upgraded sensors on ONE UNIT is 1/5 the total number of upgraded sensors on the ENTIRE satellite
This tells us that there aren't many upgraded sensors among the satellite's 30 modular units
So, let's REDRAW the diagram to start with 1 NON-upgraded sensor in each of the 30 modular units

Okay, so if there's 1 NON-upgraded sensor in EACH of the 30 modular units, then there is a TOTAL of 5 UPgraded sensors on the ENTIRE satellite.

At this point, our diagram meets all of the conditions in the question.

What fraction of the sensors on the satellite have been upgraded?
We can see that we have a total of 35 sensors, and 5 of them are upgraded.
So, the fraction = 5/35 = 1/7

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

Re: A satellite is composed of 30 modular units, each of which   [#permalink] 28 Aug 2019, 08:45
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