A pet shelter has cats, dogs and rabbits. The ratio of the number of cats to the number of dogs is 360 : 480. The ratio of the number of dogs to the number of rabbits is 8 : 5.
- Write the ratio of the number of cats to the number of dogs in its simplest form.
- Find the ratio of the number of cats to the number of rabbits in its simplest form.
- There are 90 rabbits. How many cats are there?
Need a hint?
In (a), find the largest number that divides both 360 and 480. In (b), the dog numbers must match before you can combine the two ratios.
Worked answer
- (a) Divide both 360 and 480 by 120: 360 : 480 = 3 : 4.
- (b) Make the dogs the same in both ratios: cats : dogs = 3 : 4 = 6 : 8, and dogs : rabbits = 8 : 5.
- (b) So cats : dogs : rabbits = 6 : 8 : 5, and cats : rabbits = 6 : 5.
- (c) Rabbits are 5 units, so 1 unit = 90 ÷ 5 = 18.
- (c) Cats are 6 units, so there are 6 × 18 = 108 cats.
The mistake this question tests
Simplest form in final fraction answers
Pupils often write 3 : 4 and 8 : 5 and join them directly as cats : rabbits = 3 : 5 without matching the dog units first.
How to fix it at home →More PSLE ratio questions
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