A florist sells roses, lilies and tulips. The number of roses is r. The number of lilies is 4 times the number of roses. The number of tulips is 5 fewer than the number of lilies.
- Find the total number of flowers in terms of r. Give your answer in the simplest form.
- If r = 8, find the total number of flowers.
Need a hint?
Write each flower count using r first: lilies are 4 groups of r, and tulips are 5 less than the lilies. Then add all three and collect the r terms together.
Worked answer
- Roses = r
- Lilies = 4 × r = 4r
- Tulips = 4r − 5
- Total = r + 4r + (4r − 5) = 9r − 5
- When r = 8: 9 × 8 − 5 = 72 − 5 = 67
The mistake this question tests
Collecting like terms in algebra
A common mistake is to write tulips as r − 5 or 4r + 5, mixing up '5 fewer than the lilies'. Another is forgetting to combine the r terms, leaving the answer as r + 4r + 4r − 5 instead of 9r − 5.
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