Multiple choice

A zoo has a group of 30 animals consisting of elephants and zebras. The average weight of an elephant is 6,000 kg, and the average weight of a zebra is 400 kg. If the total weight of all animals is 79,200 kg, how many elephants are there in the zoo?

  1. 8

  2. 9

  3. 10

  4. 12

  5. 15
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let E be elephants and Z be zebras. E + Z = 30, so Z = 30 - E. 6000E + 400(30 - E) = 79200. 6000E + 12000 - 400E = 79200. 5600E = 67200. E = 67200 / 5600 = 12.

AI explanation

Let the number of elephants be E and the number of zebras be Z, giving the equation E + Z = 30. Using the total weight, form the second equation 6000E + 400Z = 79200, and simplify it by dividing by 400 to get 15E + Z = 198. Subtracting the first equation from this simplified equation gives 14E = 168, so E equals 12.

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