Bride Speed 21673E
1. **State the problem:** A couple is arranging flowers for a wedding. The bride finishes one arrangement in $x$ minutes, and the groom finishes his arrangement 8 minutes later, i.e., in $x+8$ minutes. Together, they complete 40 arrangements in 3 hours (180 minutes). We need to find how fast the bride was and how many arrangements she made by herself.
2. **Set up the equation:** The rate of the bride is $\frac{1}{x}$ arrangements per minute, and the groom's rate is $\frac{1}{x+8}$. Together, their combined rate is $\frac{40}{180} = \frac{2}{9}$ arrangements per minute.
3. **Write the combined rate equation:**
$$\frac{40}{x} + \frac{40}{x+8} = 180$$
This equation is incorrect as stated; the correct approach is:
Since they complete 40 arrangements in 180 minutes, their combined rate is:
$$\frac{40}{180} = \frac{2}{9}$$
The sum of their rates is:
$$\frac{1}{x} + \frac{1}{x+8} = \frac{2}{9}$$
4. **Solve the equation:**
Multiply both sides by $9x(x+8)$ to clear denominators:
$$9(x+8) + 9x = 2x(x+8)$$
Simplify:
$$9x + 72 + 9x = 2x^2 + 16x$$
$$18x + 72 = 2x^2 + 16x$$
Bring all terms to one side:
$$0 = 2x^2 + 16x - 18x - 72$$
$$0 = 2x^2 - 2x - 72$$
Divide both sides by 2:
$$0 = x^2 - x - 36$$
5. **Factor or use quadratic formula:**
$$x = \frac{1 \pm \sqrt{1 + 144}}{2} = \frac{1 \pm \sqrt{145}}{2}$$
Since time must be positive, take the positive root:
$$x = \frac{1 + 12.0416}{2} = 6.5208$$ minutes
6. **Find how many arrangements the bride made by herself:**
The bride's rate is $\frac{1}{6.5208}$ arrangements per minute.
In 180 minutes, she would make:
$$180 \times \frac{1}{6.5208} \approx 27.6$$ arrangements
**Final answers:**
- The bride finishes one arrangement in approximately $6.52$ minutes.
- She made about $28$ arrangements by herself (rounding to nearest whole number).