chicken feed and goat feed combined

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chicken feed and goat feed combined

by Needgmat » Sat Oct 08, 2016 8:44 am
A farmer spent $35 on feed for chickens and goats. He spent 40 percent of the money on chicken feed, which he bought at a 20 percent discount off the full price, and spent the rest on goat feed, which he bought at full price. If the farmer had paid full price for both the chicken feed and the goat feed, what amount would he have spent on the chicken feed and goat feed combined?

A) $37.80

B) $38.50

C) $39.20

D) $39.50

E) 40.60

OAB

I got A. I don't know how this option is wrong.

Money spent on chicken feed = 35*40/100 = 14.

Money spent on goat feed = 35-14 = 21

Chicken bought at 20% discount = 14*20/100 = 2.80

so the total amount = 14+2.80 = 16.80

Total amount = 16.80+21 = 37.80

Please explain.
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by GMATGuruNY » Sat Oct 08, 2016 8:59 am
A farmer spent $35 on feed for chickens and goats. He spent 40% money on chicken feed, which he bought at a 20% discount off the full price, and spent the rest on goat feed, which he bought at full price. If the farmer had paid full price for both the chicken feed and the goat feed, what amount would he have spent on the chicken feed and goat feed combined?

A. $37.80
B. $38.50
C. $39.20
D. $39.50
E. $40.60
We need to determine the following ratio:
(full price)/(actual amount spent).

To determine this ratio, plug in an EASY VALUE for the full price of chicken feed.
Since the chicken feed is discounted by 20% -- the equivalent of 1/5 -- let the regular price of chicken feed = $5.

Then:
After the 1/5 discount, the amount spent on chicken feed = 5 - (1/5)*5 = 4.
Since the amount spent on chicken feed represents 40% -- the equivalent of 4/10 -- of the total amount spent, the total amount spent = $10, while the amount spent on goat feed = $6.
Resulting values:
Full price = (regular chicken feed price) + (regular goat feed price) = 5+6 = 11.
Actual amount spent = (regular chicken feed price) + (regular goat feed price) = 4+6 = 10.
Thus:
(full price)/(actual amount spent) = 11/10.

The resulting ratio implies that the full price is equal to 11/10 of the actual amount spent ($35):
(11/10) * 35 = (11/2) * 7 = 77/2 = 38.5.

The correct answer is B.
I got A. I don't know how this option is wrong.

Money spent on chicken feed = 35*40/100 = 14.

Money spent on goat feed = 35-14 = 21

Chicken bought at 20% discount = 14*20/100 = 2.80


so the total amount = 14+2.80 = 16.80

Total amount = 16.80+21 = 37.80

Please explain.
The portion is red does not accurately reflect the following statement:
He spent 40 percent of the money on chicken feed, which he bought at a 20 percent discount off the full price.
Implication of this statement:
The chicken feed purchased for $14 was bought at a 20% discount off the regular price.
Thus, the $14 spent on chicken feed constitutes 80% of the regular price for chicken feed:
14 = (80/100)x
14 = (4/5)x
x = 70/4 = 35/2 = $17.50.

Thus, the total regular price for chicken feed and goat feed = 17.50 + 21 = $38.50.
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by [email protected] » Sat Oct 08, 2016 9:36 am
Hi Needgmat,

This question is essentially about arithmetic and taking the proper notes. You can go about the math steps in a couple of different ways though - depending on how you 'see' this information.

From the prompt, we know that the farmer spent $35 on feed.... 40% of his money on chicken feed.... and the rest on goat feed. This means that for every dollar he spent, $0.40 was spent on chicken feed and $0.60 was spent on goat feed. With a total of $35 spent, we can easily break down the two totals....

(.4)($35) = $14.00 on chicken feed
The rest = $35 - $14 = $21 on goat feed

We were also told that the chicken feed was purchased at a 20% discount, which means that the farmer paid 80% of the regular price for that feed.

$14.00 = (.8)(Regular Price)
$14/.8 = (Regular Price)
$140/8 = (Regular Price)
$17.50 = (Regular Price)

We're asked what the price would have been if the farmer had bought both feeds at full price.... $21 + $17.50 = $38.50

Final Answer: B

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by Brent@GMATPrepNow » Sun Oct 09, 2016 7:22 am
A farmer spent $35 on feed for chickens and goats. He spent 40% of the money on chicken feed, which he bought at a 20% discount off the full price, and spent the rest on goat feed, which he bought at full price. If the farmer had paid full price for both the chicken feed and the goat feed, what amount would he have spent on the chicken feed and goat feed combined?

A. $37.80
B. $38.50
C. $39.20
D. $39.50
E. $40.60
He spent 40% (of the $35) on chicken feed.
40% of $35 = $14. So, he spent $14 on chicken feed.

He got a 20% discount on the chicken feed.
In other words, he paid 80% of the original price.
So, let C = original price of chicken feed.
We can write 80% of C = $14
Or we can write 0.8C = $14
Or, even better, (4/5)C = $14

To solve for C, we'll multiply both sides by 5/4 to get: C = (14)(5/4) = 17 1/2
So, the original price of the chicken feed = $17.5

Finally, if the farmer spent $14 (of the original $35) on chicken feed, then he spent the remaining $21 on goat feed (at no discount).

So, without the discount, the farmer would have paid $17.5 + $21 =[spoiler] $38.50 = B[/spoiler]

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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