There are some donkeys, hens and donkeys in a farm.There are 5 times as many hens as donkeys. Barbara finds out that among the animals, there are a total of 30 heads and 90 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
|
15
|
15 x 4 =
60 |
15
|
15 x 2 =
30 |
30 |
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 - 90
= 30
Small difference between one 2-legged animal and one 4-legged animal
= 4 - 2
= 2
Number of hens
= 30 ÷ 2
= 15
Number of 4-legged animals
= 30 - 15
= 15
Number of donkeys = 1 u
Number of hens = 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of donkeys
= 1 u
= 3
Number of donkeys
= 15 - 3
= 12
Answer(s): 12
