In the Singapore zoo, there are deers and there are ducks. If the head

Question

In the Singapore zoo, there are deers and there are ducks. If the heads are counted, there are 180, while the legs are 448. What will be the number of deers in the zoo?

A. 136
B. 68
C. 44
D. 22
E. 20

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Rabab36 · Answer

let x be deer and y be ducks we get 2 eq
x+y=180
and 
2x+4y=448

solving we get y=44

option c
correct

hinasingh · Answer

In the Singapore zoo, there are deers and there are ducks. If the heads are counted, there are 180, while the legs are 448. What will be the number of deers in the zoo?
Let x be number of deers and y be number of ducks
then, x + y = 180 and 4x + 2y = 448 
=> 2x + y = 224 
=> 2x + 180 -x = 224 (substitute y = 180 -x)
=> x = 44
Answer C

wickedvikram · Answer

C

Deers=x; ducks=y
x+y=180
4x+2y=448

x=44

Abhishek009 · Answer

Consider that there are 180 animals and all have 4 legs each, thus total no of legs is 180*4 = 720

However , there are 448 legs or, 272 less legs, this is because we have counted 2 legs extra for the ducks (Since they have 2 legs each)

So, No of ducks is 272/2 = 136, Answer must be (A)

ThatDudeKnows · Answer

Abhishek009 An elegant solution

...to a different question...this one asks for the number of deers !

The trap that Abhishek fell into is one of the most common that test writers employ. If you fall into it once or twice, chalk it up to a learning experience. If you fall into it more than that, it's no longer a silly mistake; it's a pattern. And if you know that you're prone to fall into a specific trap, you need to take steps to avoid doing so on test day. Here's a trick for this one. First, before you start solving any multi-variable question, pause for two seconds and see which variable you're being asked for. If there's a reasonably straightforward way to solve directly for that variable first (rather than solving for a different variable and then having to plug back in to find the one the question asks for), do that. In this case, Abhishek could have started with, "Consider that there are 180 animals and all have TWO legs each,..." That would have allowed him to solve directly for the number of deers. If solving for the desired variable is not so straightforward and you're going to need to solve for a different one first, do something with your testing environment that serves as a reminder to make sure you've solved for the correct variable before you click an answer choice. My favorite is to flip over my computer mouse as soon as I spot that the test writer is using this trap or any other trap. When I go to click my answer, the upside-down mouse reminds me to make sure I've accounted for the trap. If you're on a laptop, use something to cover either the touchpad or the area of the screen that has the button to confirm your answer choice...that way you can't answer until you are reminded to make sure avoided the trap. This mistake, by a user who has a pretty good handle on "real" math, is an example of why I prefer to avoid "real" math on standardized tests. If (i) the instinct is to set up an algebraic equation and introduce a variable (or more than one variable) that isn't in the question and (ii) the answers are just numbers, there's a great chance we can get the answer just as fast and with almost no room for a silly mistake or falling in a trap like this one using Plugging In The Answers (PITA). I like trying B and D. B: 68 deers means 112 ducks. 68*4 + 112*2 = 272 + 224 = 496 legs. That's too many legs. D: 22 deers means 158 ducks. 22*4 + 158*2 = 88 + 316 = 404 legs. That's not enough legs. We need something between those two. Answer choice C. ThatDudeKnowsPITA ThatDudeKnowsPluggingInTheAnswers

Abhishek009 · Answer

ThatDudeKnows

By bad, in a hurry while replying from office , concluded pretty soon, thanks for pointing the same.

In the Singapore zoo, there are deers and there are ducks. If the head

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In the Singapore zoo, there are deers and there are ducks. If the head

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

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My Rewards