A tailor has 45 white buttons and 75 black buttons. What is the ratio of the number of white buttons to the number of black buttons in its simplest form?
- 3 : 5
- 5 : 3
- 9 : 15
- 45 : 75
Need a hint?
Look for the largest number that divides into both 45 and 75 exactly.
Worked answer
- Find the highest common factor of 45 and 75, which is 15.
- Divide both numbers in the ratio by 15: 45 ÷ 15 = 3 and 75 ÷ 15 = 5.
- The ratio in simplest form is 3 : 5.
Answer: 3 : 5
The mistake this question tests
Habit
Simplest form in final fraction answers
Dividing by a common factor such as 5 only gives 9 : 15, which is equivalent but not in simplest form, since 9 and 15 can still both be divided by 3.
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