Ai Tong School P5 Math CA1 2006 (Q39)

Lincoln visited a farm where he saw some cows and ducks. There were 75 of them. He then counted the legs of the animals and found that there were 220. How many animals of each type were there in the farm?

Solution

If we assume all the animals were ducks

75 animals x 2 legs ----- 150 legs

But there were 220 legs. A cow has 2 “more legs” than a duck.

220 legs – 150 legs ----- 70 “more legs”

2 “more legs” ----- 1 cow

1 “more leg” ----- 1 divided by 2 = ½

70 “more legs” ----- ½ x 70 = 35

If there were 35 cows, the number of ducks were

75 – 35 = 40

Answer: There were 35 cows and 40 ducks.