Question: 4. Kiran buys supplies for the school’s greenhouse. He buys $f$ bags of fertilizer and $p$ packages of soil. He pays 5 for each bag of fertilizer and 2 for each package of soil, and spends a total of 90. The equation $5f + 2p = 90$ describes this relationship.
If Kiran solves the equation for $p$, which equation would result?
A. $2p = 90 - 5f$
B. $p = \frac{5f - 90}{2}$
C. $p = 45 - 2.5f$
D. $p = \frac{85f}{2}$
1. **State the problem:** We have the equation $$5f + 2p = 90$$ and want to solve for $p$.
2. **Isolate $p$:** Subtract $5f$ from both sides:
$$5f + 2p - 5f = 90 - 5f$$
which simplifies to
$$2p = 90 - 5f$$
3. **Divide both sides by 2 to solve for $p$:**
$$p = \frac{90 - 5f}{2}$$
4. **Simplify the fraction:**
$$p = \frac{90}{2} - \frac{5f}{2} = 45 - 2.5f$$
5. **Interpretation:** The correct equation for $p$ is $$p = 45 - 2.5f$$ which corresponds to option C.
**Final answer:** C. $p = 45 - 2.5f$