Adam has a total of 12 ducks and sheep.
The difference in their number of legs is 6.
How many (a) sheep and (b) ducks does Adam have?
Number of
ducks |
Number of
ducks' legs |
Number of
sheep |
Number of
sheep' legs |
Difference in the
number of legs |
| 12 |
12 x 2 =
24 |
0 |
0 x 4 =
4 |
24 - 0 =
24 |
| 11 |
11 x 2 =
22 |
1 |
1 x 4 =
4 |
22 - 4 =
18 |
| 9 |
9 x 2 =
18 |
3 |
9 x 4 =
12 |
18 - 12 =
6 |
If all of the animals are ducks,
the number of legs needed
= 12 x 2
= 24
Total difference in the number of legs
= 24 - 6
= 18
Difference in the number of legs when 1 duck is replaced by 1 sheep
= 24 - 18
= 6
Number of sheep
= 18 ÷ 6
= 3 (a)
Number of ducks
= 12 - 3
= 9 (b)
Answer(s): (a) 3; (b) 9
