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

Question

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. 1/24

A. 5/6
B. 1/5
C. 1/6
D. 1/7
E. 1/24

jagdeepsingh1983 · Accepted Answer

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. 1/24

No of Units-30
Let there T-Total no of sensor
U-no of upgraded sensors in one unit
Nu-No of Not upgraded senor in one unit

T= 30U+30Nu

Now we know that Nu=1/5 (30U)= 6U

So Total= 30U+30*6U = 30U+180U= 210U

Fraction= 30U/210U = 1/7  Answer is D

Regards
Jagdeep 
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BrentGMATPrepNow · Answer

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

Answer:  D

Cheers,
Brent

Spidy001 · Answer

number of non upgraded sensors per unit = 1/5 (U)
 where U is the total number of upgraded sensors in 30 units.

=> number of non upgraded sensors in 30 units = N= 30*(1/5)U= 6U

total number of sensors = U + N = U+6U = 7U

=> upgraded is U/(7U) fraction of the total = 1/7

Answer is D.

Cares · Answer

Does anyone else find this problem hard to understand and translate into an equation? I understand it clearly after the explanation but I think it is poorly worded.

sanjoo · Answer

Bunuel..i got this question wrong in my MGMAT TEST.. will u send me some liink of question like this?? I got confused when i saw fraction question like this..and hard percentage question.. Thank u

EvaJager · Answer

Not really poorly worded, but maybe lengthy, and all those words, upgraded and non-upgraded... Annoying a little bit.

If N is the number of non-upgraded sensors in every one of the 30 units, and U is the number of those upgraded, we can write N = (1/5)*30U = 6U.
This is the key equation, it is the translation of the information " ...the number of non-upgraded sensors on one unit is 1/5 the total number of upgraded sensors on the entire satellite...".
So, we have U upgraded sensors and 6U non-upgraded ones, which means that the upgraded sensors represent U/7U = 1/7 from the total number of sensors.
No need to multiply by 30, we are given that each unit has the same number of sensors of each type. Anyway, if you multiply by 30, it will cancel out and the final ratio is the same 1/7.

Answer D.

highdiving · Answer

The question needs to be read very carefully and under timed conditions it's very easy to lose track with the wording; in the review of my Mgmat exam is ranked as 700-800 level by the way, so maybe it needs to be somewhat painful

PareshGmat · Answer

Lets say total no. of upgraded sensors on whole satellite = 30
Then each module will have 1 upgraded sensor ......... (1)
 \frac{1}{5} th of 30 = 6  non-upgraded sensor on each module....... (2)

Total sensors in one module = (1) + (2)

= 6+1 = 7

Total sensors on all 30 modules = 30 * 7 = 210

Fraction = \frac{30}{210} = \frac{1}{7}

Answer = D

ashsim · Answer

Thanks for the explanations on this question! It took me a while to understand this question - the wording kept throwing me off. I finally approached it as below:

There are 30 Units, each with multiple sensors.

Sensors are either U or NU
Total number of sensors = total U + total NU

Given that total NU = 1/5 U; then 5NU = U
Also, there are same number of NUs in each unit; therefore 30NUs in total

Now plugging into the first equation:
Total sensors = 5NU + 30 NU = 35 NU

Question asks for total U/total sensors = 5NU/35NU = 1/7

Hope this helps!

GSBae · Answer

A slightly different approach:

Let x be the number of non-upgraded sensors on a single unit (which is the same for all units). Therefore, there are 30x non upgraded units on the entire satellite.

We also know that the number of non-upgraded units on a single unit (which is x) is 1/5 the total number of upgraded sensors. Therefore, 5x equals the total number of upgraded units.

Thus, to find the fraction that have been updated, we simply take upgraded/total, which is 5x/ (30x+5x) = 5/35 = 1/7.

Answer: D

hak15 · Answer

Let "n" be total number of set sensors in each unit and 'x' non- upgraded sensors.(n-x) upgraded ones.Thus,

x=1/5(n-x)(30)
Solving,
x=6/7n
There fore 1-6/7=1/7 upgraded ones

BrainLab · Answer

30 Units
Upgraded: U, means total #of Upgraded = 30*U
Non-Upgraded: N
 N=0.2*30*U  ->  \frac{U}{N}=\frac{1}{6} ,  \frac{U}{ALL}=\frac{1}{7} 
Answer D

Temurkhon · Answer

let: 
x - all upgraded 
y - all non-upgraded

what is x/x+y?

y/30=(1/5)x

y/30=x/5, so x=(1/6)y

(1/6)y/(1/6)y+y => (1/6)y/(7/6)y=1/7

D

gracie · Answer

let u=total upgraded sensors
let n=total non-upgraded sensors
u/5=n/30
u/n=1/6
u/(n+u)=1/7

yash88 · Answer

Please advise if this is wrong:

Let, upgraded sensors be: U
Non upgraded senseors be: NU

Total= U+NU

Now., NU=(1/5)U
 
Hence,

Total = U+(1/5)U
 = (6/5)U

U=(5/6)Total

So, wont the answer be A.

chetan2u · Answer

Hi,
You have gone wrong on NU = (1/5)U...
It is NU per sensor, so NU/30=(1/5)U.....NU=30/5*U=6U..

Total = U+NU= U+6U=7U..
Therefore fraction of upgraded = U/7U=1/7...

AmritaSarkar89 · Answer

Extremely tricky wording. I hope I don't encounter something like this on my actual exam.

I really did not understand it at al Bunuel  please help

manishtank1988 · Answer

NUS - non upgraded sensors 
US - upgraded sensors

mohd_int · Answer

What I am missing

Let say the total set of sensors in each unit is 5

so the total is 5*30 = 150

1/5 of the sensors that are not upgraded is 1/5 * 150 = 30

30/150 =1/5 which is not 1/7

Please, could anyone help me with this?

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