Question

400 students attend ridgewood junior high school. 25% of students bring their lunch to school every day. how many students brought their lunch to school on thursday? insert the values given in the problem then scale up or down to find the missing value. students 16 100 percent

Explanation:

Step1: Understand the problem

We know the total number of students is 400, and 25% of them bring lunch. We can also use the ratio from the tape diagram. The bottom tape has 100 (representing 100%) and the top has a value related to the number of students. First, find what percentage 16 students represent.
Let the percentage for 16 students be \( x \). We know that when the percentage is 100%, the number of students is 400? Wait, no, the tape diagram: the bottom is percent (100 at the end) and top is students. Wait, maybe the ratio is that 100% corresponds to 400 students? Wait, no, the problem says 400 students total. Let's use the percentage method first. 25% of 400.

Step2: Calculate 25% of 400

To find a percentage of a number, we use the formula: \( \text{Part} = \text{Percentage} \times \text{Total} \). Here, the percentage is 25% (or 0.25 in decimal), and the total is 400. So \( 0.25 \times 400 = 100 \)? Wait, no, 25% of 400 is \( \frac{25}{100} \times 400 = 100 \)? Wait, no, 25% is a quarter, so 400 divided by 4 is 100? Wait, but let's check the tape diagram. The bottom tape: the right end is 100 (percent), and the top tape: when the bottom is 100 (percent), the top should be 400? No, the top has 16 at some point. Wait, maybe the tape diagram is showing a ratio. Let's see: if 100% (bottom) corresponds to 400 students (top), then what percentage does 16 students correspond to? Let \( x \) be the percentage for 16 students. Then \( \frac{16}{400} = \frac{x}{100} \). Solving for \( x \): \( x = \frac{16 \times 100}{400} = 4\% \). So 16 students is 4% of the total. Then, we need 25% of the students. Since 4% is 16 students, then 1% is \( \frac{16}{4} = 4 \) students. Then 25% is \( 25 \times 4 = 100 \) students. Wait, that matches the percentage calculation. So the missing value on the top tape (at the 100% mark on the bottom) should be 400? No, wait the problem is asking how many students brought lunch on Thursday, which is 25% of 400. Wait, 25% of 400 is 100? Wait, no, 25% of 400: 400 0.25 = 100? Wait, 400 0.25: 400 1/4 = 100. Yes. Alternatively, using the tape diagram: the bottom is percent (100 is 100%), top is students. We know that 4% (from 16 students) is 16, so 25% would be (25 / 4) 16 = 100. So the number of students who brought lunch is 100? Wait, but let's confirm. The total students are 400, 25% bring lunch: 0.25 * 400 = 100. Yes.

Answer:

100