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Mix 72 litres in the ratio 2:7
To make a green paint, blue and yellow are mixed in the ratio 2:7, and 72 litres of paint are needed in total. How many litres of each colour are needed?
Answer
Split in the ratio 2:7 → 16 and 56
Step-by-step
- 2 + 7 = 9Total parts = sum of all ratio terms
- 72 ÷ 9 = 8Value of one part
- 8 × 2 = 16Share for ratio term 1
- 8 × 7 = 56Share for ratio term 2
Why it works
Sharing in a ratio means splitting the total into 2 + 7 = 9 equal parts; one part is the total divided by 9, and each share is that part multiplied by its own number of parts.
Common mistakes
- Dividing 72 by 7 instead of by the 2 + 7 = 9 parts in total.
- Using 72 ÷ 2 = 36 as the size of one part.