<PRE><B>Question 1210285</B>
&lt;br&gt;
First a typical standard algebraic solution....&lt;br&gt;
p = # of pigs
c = # of chickens&lt;br&gt;
Each pig has four feet and each chicken has two; each pig and each chicken has one head.&lt;br&gt;
The total number of heads is 27:
p+c = 27 [1]&lt;br&gt;
The total number of feet is 78:
4p+2c = 78 [2]&lt;br&gt;
Solve the pair of equations [1] and [2] by your favorite method.  When the two equations are in this form, elimination is my preference.&lt;br&gt;
Multiply equation [1] by 2 and compare to equation [2] to eliminate c and solve for p.&lt;br&gt;
2p+2c = 54
4p+2c = 78
2p = 78-54 = 24
p = 24/2 = 12&lt;br&gt;
The number of pigs is 12, so the number of chickens is 27-12 = 15.&lt;br&gt;
ANSWER: 12 pigs, 15 chickens&lt;br&gt;
And now an informal solution, done mentally and quickly.&lt;br&gt;
If all 27 animals were chickens, the number of feet would be 27*2 = 54.
The actual number of feet is 78, which is 24 more than that.
Each pig has 2 more feet than each chicken, so the number of pigs is 24/2 = 12.&lt;br&gt;
ANSWER: 12 pigs and 17-12 = 15 chickens&lt;br&gt;
For studying math, understanding the formal algebraic solution is important.&lt;br&gt;
But solving problems like this informally using logical reasoning is excellent brain exercise.&lt;br&gt;
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