The problem involves analyzing data from a bar graph and two pie charts showing the number of books borrowed from a library by fifth-grade students from September to December. The first task is to determine which data from the bar graph and pie charts are needed to calculate the number of books borrowed in October and the number of history books borrowed in September. The second task is to explain why it's incorrect to assume the number of story books borrowed in September and December are the same, even if the percentage of story books is the same for both months.

1. Problem Description

The problem involves analyzing data from a bar graph and two pie charts showing the number of books borrowed from a library by fifth-grade students from September to December. The first task is to determine which data from the bar graph and pie charts are needed to calculate the number of books borrowed in October and the number of history books borrowed in September. The second task is to explain why it's incorrect to assume the number of story books borrowed in September and December are the same, even if the percentage of story books is the same for both months.

2. Solution Steps

First, let's identify the information needed to answer the first two questions.

For part 1:

To find the number of books borrowed in October, we need to look at the bar graph. The relevant data is at position "ア". So the answer to the first question is "ア",

1

0

0. For part 2:

To find the number of history books borrowed in September, we need to know the total number of books borrowed in September and the percentage of history books. From the bar graph we know that the number of books borrowed in September corresponds to position "ア", and from the pie chart we know that the relative amount of history books borrowed corresponds to position "カ". So the answer to the second question is "ア" and "カ".

The total number of books borrowed in September is

1

0

0. The pie chart shows that history books account for 50% of the books borrowed in September.

$0.50 \times 100 = 50$. Therefore, the number of history books borrowed in September is

5

0.

Now let's address the third task.

The pie charts show the percentage of story books for September and December. The problem states that the percentages are the same. By observation we can see that the percentage is 40%. However, the total number of books borrowed is different for each month.

Total books borrowed in September: 100

Total books borrowed in December: 120

Number of story books in September: $100 \times 0.4 = 40$

Number of story books in December: $120 \times 0.4 = 48$

The percentage of story books is 40% in both months.

The total number of books borrowed in September is

1

0

0. The total number of books borrowed in December is

1

2

0. Therefore, the number of story books borrowed in September is $100 \times 0.4 = 40$.

And, the number of story books borrowed in December is $120 \times 0.4 = 48$.

The number of story books in December is higher.

3. Final Answer

1. 記号: ア, 答え: (100)

2. 記号: ア と カ, 答え: (50)

3. 9月と12月の物語の割合は40%で同じですが、9月の全体のさっ数は100さつ、12月の全体のさっ数は120さつです。全体のさっ数がちがうので、物語のさっ数もちがいます。

9月の物語のさっ数は、100×0.4=40で、40さつです。12月の物語のさっ数は、120×0.4=48で、48さつです。12月の方が物語のさっ数は多いです。