In Goshawk-Eurasian nature reserve 30 percent of the birds

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AAPL: Moderator; Posts: 2599; Joined: Sun Oct 29, 2017 2:08 pm; Followed by:2 members

In Goshawk-Eurasian nature reserve 30 percent of the birds

by AAPL » Tue Aug 27, 2019 5:59 am

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Economist GMAT

In Goshawk-Eurasian nature reserve 30 percent of the birds are Hawks, and 40 percent of the non-Hawks are Paddyfield-Warblers. If there are 25 percent as many Kingfishers as Paddyfield-Warblers in the reserve, then what percent of the birds in the nature reserve are not Hawks, Paddyfield-Warblers, or Kingfishers?

A. 25%
B. 35%
C. 45%
D. 70%
E. 80%

OA B

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Source: Beat The GMAT — Problem Solving | Tue Aug 27, 2019 5:59 am

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Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 am; Location: Grand Central / New York; Thanked: 470 times; Followed by:34 members

by Jay@ManhattanReview » Wed Aug 28, 2019 10:41 pm

AAPL wrote:Economist GMAT

In Goshawk-Eurasian nature reserve 30 percent of the birds are Hawks, and 40 percent of the non-Hawks are Paddyfield-Warblers. If there are 25 percent as many Kingfishers as Paddyfield-Warblers in the reserve, then what percent of the birds in the nature reserve are not Hawks, Paddyfield-Warblers, or Kingfishers?

A. 25%
B. 35%
C. 45%
D. 70%
E. 80%

OA B

Say there are 100 birds in the reserve. Thus, there are 30 Hawks and 100 - 30 = 70 non-Hawks. Given 40 percent of the non-Hawks are Paddyfield-Warblers, there are 40% of 70 = 28 Paddyfield-Warblers. Thus, there are 70 - 28 = 42 non-hawk, non-Paddyfield-Warblers birds.

Again, given there are 25 percent as many Kingfishers as Paddyfield-Warblers, there are 25% of 28 = 7.

Thus, there are 42 - 7 = 35 non-hawk, non-Paddyfield-Warblers birds in the reserve.

The correct answer: B

Hope this helps!

-Jay
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deloitte247: Legendary Member; Posts: 2214; Joined: Fri Mar 02, 2018 2:22 pm; Followed by:5 members

by deloitte247 » Fri Aug 30, 2019 11:37 pm

Let the total number of birds = b
Hawks = 30% of b = 30/100 rb = 0.3b
Non hawks = ( 100 - 30 )% of b = 70% of b
= 70/100 * b = 0.7b
Paddyfield warblers = 40% of non hawks
= 40% of 0.7b = 40/100 * 0.7 * b
= 0.4 * 0.7 * b = 0.28b
Kingfishers = 25% of paddyfield warblers
= 25/100 * 0.28b = 0.25 * 0.28 * b
= 0.07b
% of birds in the nature reserve that are not hawks paddyfield-warblers or kingfishers =>
Let b = 100
Hawks = 0.3 * 100 = 30
Paddyfield-warblers = 0.28 * 100 = 28
Kingfishers = 0.07 * 100 = 7
Total number of birds that are not hawks, paddyfield or kingfishers
= total birds - hawks - paddtfield - kingfishers
= 100 - 30 - 28 - 7 = 35
Answer = option B

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Mon Sep 02, 2019 5:54 pm

AAPL wrote:Economist GMAT

In Goshawk-Eurasian nature reserve 30 percent of the birds are Hawks, and 40 percent of the non-Hawks are Paddyfield-Warblers. If there are 25 percent as many Kingfishers as Paddyfield-Warblers in the reserve, then what percent of the birds in the nature reserve are not Hawks, Paddyfield-Warblers, or Kingfishers?

A. 25%
B. 35%
C. 45%
D. 70%
E. 80%

OA B

We can let the total number of birds in the nature reserve be 100. Thus, we have 30 hawks, 0.4(70) = 28 paddyfield-warblers and 0.25(28) = 7 kingfishers. Therefore, 100 - (30 + 28 + 7) = 35, or 35%, of the birds are none of these three types of birds.

Answer: B

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