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Algebra Level 2

In a zoo, there are rabbits and pigeons. If heads are counted, there are 340 heads and if legs are counted there are 1060 legs. How many pigeons are there?


The answer is 150.

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2 solutions

Steven Jin
Aug 1, 2014

While this problem can be easily done using a system of equations (as Krishna's solution states), this problem is also solvable by a bit of slick thinking.

We first assume that the zoo is all pigeons; that is, we assume that there are 340 340 pigeons. Clearly, this will fail to fulfill the legs requirement; in this case, we're 1080 ( 2 × 340 ) = 380 1080 - (2 \times 340) = 380 legs short.

We then note that by replacing a pigeon with a rabbit, we essentially "add" two legs. Thus, to fulfill the legs requirement, we need to replace 380 / 2 = 190 380 / 2 = 190 pigeons with rabbits. Thus, we have 190 190 rabbits and 150 \boxed{150} pigeons.

Krishna Priya R
Jul 31, 2014

Let the no. of rabbits be X

and the no. of pigeons be Y

since both of them have 1 head apiece, X+Y=340.

Rabbits have 4 legs and Pigeons have 2 legs so, 4X+2Y=1060.

Solving for Y we get Y= 150.

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