Brain Teasers
Reptile House
At a recent visit to the reptile house at the local zoo, I counted a total of 27 heads and 70 feet. I was counting snakes, lizards, and people. I know that there were exactly twice as many lizards as people. How many snakes did I count?
Answer
6 snakes, 7 people, and 14 lizards.Hide Answer Show Answer
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When I read the problem, I thought of 2 equations but you only need to solve 1.
If x = people, total legs are
2x + 2x*4 = 70
If x = people, total legs are
2x + 2x*4 = 70
Since there are twice as many lizards as people, each group of
2 lizards and 1 person has 10 feet and 3 heads. Since the snakes have
no feet, there must be 7 such groups to account for the 70 feet, leaving
6 heads unaccounted for that must be snakes.
2 lizards and 1 person has 10 feet and 3 heads. Since the snakes have
no feet, there must be 7 such groups to account for the 70 feet, leaving
6 heads unaccounted for that must be snakes.
Or to put it another way.. initially assume there are no people. Then there are no lizards an no legs. If there is 1 person, then there are 2 lizards and 10 legs. Each extra person adds 10 legs. We need 70 legs so that's 7 people , 14 lizards and 6 snakes.
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