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Data Sufficiency - Not Clear

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Data Sufficiency - Not Clear

by clawhammer » Fri Oct 22, 2010 8:53 pm
Is this question clear to you:

At a laboratory, white rats are fed 6 pellets of food per day and black rats are fed 8 pellets of food per day. If the laboratory fed a total of 120 pellets of food to white and black rats on a certain day, were more black rats than white rats fed?

1. There is a total of 17 rats.
2. There are 8 white rats.


Please explain how you get an answer for this. I'm confused with the question.
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by frank1 » Fri Oct 22, 2010 9:15 pm
clawhammer wrote:Is this question clear to you:

At a laboratory, white rats are fed 6 pellets of food per day and black rats are fed 8 pellets of food per day. If the laboratory fed a total of 120 pellets of food to white and black rats on a certain day, were more black rats than white rats fed?

1. There is a total of 17 rats.
2. There are 8 white rats.


Please explain how you get an answer for this. I'm confused with the question.
well best of i can think of for now
it is not asking who has more power to eat
it is asking of 120 food available,in given group does x consumed more than y(x has power of 6 and y has power of 8)
now if there were
more y or equal numbers of x and y in group ,sure y will win
but if there were
2=y and may be 12=x with greater force x will consume more in totality(though its per entity consumption rate is lower than y)
so we need to know numbers of white rat and black rat in group
so
from question
6W+8R=120

statement 1)
w+r=17
solving we have w and r and how much each consumes.We can answer question.
sufficient

statement 2
w=8
ie
6x8+8r=120
we have how much 8r will consume so sufficient

so D

What is source of question by the way.

thanks
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by Rezinka » Fri Oct 22, 2010 9:20 pm
The question says :

White rats are fed 6 pellets of food per day.
So, if there are 'w' white rats, in a day food fed to them = 6w

Also,
black rats are fed 8 pellets of food per day.
So, if there are 'b' black rats, in a day total food fed to them = 8b

Also,
120 pellets of food was the total food fed on a certain day.

On any day, total food fed = 6w+8b (from above)
so, 6w + 8b = 120

We have 1 equation and 2 unknowns. So, if we can find another equation we have the answer.

Analysing the options ;

1. total rats = 17
or, (no. of white rats) + (no. of black rats) = 17
or, w+ b = 17
we have 2 equations...................................................... SUFFICIENT

2. white rats = 8
or, w = 8
so, we can calculate the number of black rats............... SUFFICIENT


ANS : D
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by clawhammer » Fri Oct 22, 2010 9:27 pm
Rezinka wrote:The question says :

so, 6w + 8b = 120

We have 1 equation and 2 unknowns. So, if we can find another equation we have the answer.

ANS : D
Thanks to both of you. it makes sense. I was thinking of adding 6+8 as well, so I could say:

6/14 = w/ 120

Can you please tell me where I'm making the mistake?
This part got me confused!

BTW: Source is Kaplan, OA is D.
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by Rezinka » Fri Oct 22, 2010 11:01 pm
You cannot equate 14 to 120 because :

120 = (no. of black rats x no. of food pellets to black rats per day) + ( no. of white rats x no. of food pellets to white rats per day)

14 = no. of food pellets to black rats per day + no. of food pellets to white rats per day)

These are 2 different quantiites with different dimensions.
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by limestone » Sat Oct 23, 2010 3:00 am
Hi,

1. If the no. of black rats is equal to the no. of white rats, then the average no. of pellets fed to them will be : (8+6)/2 = 7

However, in this case, the average no. of pellets is : 120/17 = 7 + 1/7 = something greater than 7.

Hence, the no. of black rats - who eat 8 pellets per day - must be greater than the no. of white rats - who eat 6 pellets per day.

Thus 1 is Suff.

2. We know the no. of white rats, so we can find how many pellets they eat per day. Then we can calculate how many pellets black rats eat per day. Finally, we can find the no. of black rats. Compare the two numbers of rats => suff. ( you should stop here to save time)

The equation is: ( solve this for the sake of finding specific figures only)
No. of black rats : (120-8*6)/8 = 9
And 9>8

Hence 2 is also suff.

Pick D.
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