Adam has a total of 13 ducks and donkeys.
The difference in their number of legs is 8.
How many (a) donkeys and (b) ducks does Adam have?
Number of
ducks |
Number of
ducks' legs |
Number of
donkeys |
Number of
donkeys' legs |
Difference in the
number of legs |
| 13 |
13 x 2 =
26 |
0 |
0 x 4 =
4 |
26 - 0 =
26 |
| 12 |
12 x 2 =
24 |
1 |
1 x 4 =
4 |
24 - 4 =
20 |
| 10 |
10 x 2 =
20 |
3 |
10 x 4 =
12 |
20 - 12 =
8 |
If all of the animals are ducks,
the number of legs needed
= 13 x 2
= 26
Total difference in the number of legs
= 26 - 8
= 18
Difference in the number of legs when 1 duck is replaced by 1 donkey
= 26 - 20
= 6
Number of donkeys
= 18 ÷ 6
= 3 (a)
Number of ducks
= 13 - 3
= 10 (b)
Answer(s): (a) 3; (b) 10
