Use the top-level ratio 4:5 to find how many roses and sunflowers there are, then break each group down using sub-ratios.
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• Top-level ratio 4:5 means 9 units in total.
• 72 ÷ 9 = 8 per unit.
• Roses: 4 × 8 = 32
• Sunflowers: 5 × 8 = 40
For the roses (sub-ratio 7 + 1):
• 8 parts = 4 per part
• blooming: 7 × 4 = 28
• wilting: 1 × 4 = 4
For the sunflowers (sub-ratio 4 + 1):
• 5 parts = 8 per part
• blooming: 4 × 8 = 32
• wilting: 1 × 8 = 8
Total blooming: 28 + 32 = 60.
Check: 32 + 40 = 72 = total (72). ✓
Final Answer: 60