There are some donkeys, geese and cows in a farm.There are 3 times as many geese as cows. Tammy finds out that among the animals, there are a total of 30 heads and 78 legs. How many donkeys are there?
Number of
4-legged animals |
Total legs of
4-legged animals |
Number of
2-legged animals |
Total legs of
2-legged animals |
Total legs |
30
|
30 x 4 =
120 |
0
|
0
|
120
|
29
|
29 x 4 =
116 |
1
|
1 x 2 =
2 |
118
|
9
|
9 x 4 =
36 |
21
|
21 x 2 =
42 |
42 |
Total number of legs if all are 4-legged animals
= 4 x 30
= 120
Big difference between all the 2-legged animals and all the 4-legged animals
= 120 - 78
= 42
Small difference between one 2-legged animal and one 4-legged animal
= 4 - 2
= 2
Number of geese
= 42 ÷ 2
= 21
Number of 4-legged animals
= 30 - 21
= 9
Number of cows = 1 u
Number of geese = 3 u
3 u = 21
1 u = 21 ÷ 3 = 7
Number of cows
= 1 u
= 7
Number of donkeys
= 9 - 7
= 2
Answer(s): 2
