A barn contains only chickens and cows. Looking inside, you count 30 heads and 84 legs in total. How many cows are in the barn?
12 cows
Let C be chickens and W be cows. C + W = 30 and 2C + 4W = 84. Multiplying the first equation by 2 gives 2C + 2W = 60. Subtracting this from the second equation yields 2W = 24, so W = 12 cows.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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