Adam has a total of 10 ducks and pigs.
The difference in their number of legs is 8.
How many (a) pigs and (b) ducks does Adam have?
Number of ducks |
Number of ducks' legs |
Number of pigs |
Number of pigs' legs |
Difference in the number of legs |
10 |
10 x 2 = 20 |
0 |
0 x 4 = 4 |
20 - 0 = 20 |
9 |
9 x 2 = 18 |
1 |
1 x 4 = 4 |
18 - 4 = 14 |
8 |
8 x 2 = 16 |
2 |
8 x 4 = 8 |
16 - 8 = 8 |
If all of the animals are ducks,
the number of legs needed
= 10 x 2
= 20
Total difference in the number of legs
= 20 - 8
= 12
Difference in the number of legs when 1 duck is replaced by 1 pig
= 20 - 14
= 6
Number of pigs
= 12 ÷ 6
= 2 (a)
Number of ducks
= 10 - 2
= 8 (b)
Answer(s): (a) 2; (b) 8