To address the problem, we need to follow a step-by-step approach:
1. Understand the problem: We know that 5 students use 18 pencils in 9 days. We need to calculate how many days 66 pencils will last for 15 students at the same usage rate.
2. Calculate the usage rate:
- First, find out how many pencils a single student uses per day.
- The total number of pencils used by all students per day is [tex]\( \frac{18 \text{ pencils}}{9 \text{ days}} = 2 \text{ pencils/day} \)[/tex].
- Therefore, each student uses [tex]\( \frac{2 \text{ pencils/day}}{5 \text{ students}} = 0.4 \text{ pencils per student per day} \)[/tex].
3. Apply the usage rate:
- If each student uses 0.4 pencils per day, 15 students will use [tex]\( 15 \text{ students} \times 0.4 \text{ pencils per student per day} = 6 \text{ pencils per day} \)[/tex].
4. Determine the duration:
- We need to find out for how many days 66 pencils will last for 15 students using 6 pencils per day.
- The number of days can be calculated by dividing the total number of pencils by the number of pencils used per day: [tex]\( \frac{66 \text{ pencils}}{6 \text{ pencils per day}} = 11 \text{ days} \)[/tex].
Conclusion:
66 pencils will last for 15 students for 11 days at the same usage rate.
