The pie chart shows how Michael spent his money.

1. Identify the fraction of the pie chart representing the book

The sector for the book has a right angle ($90^\circ$), which represents $\frac{90}{360} = \frac{1}{4}$ of the total pie chart.

2. Determine the fraction representing the rest of the items

The remaining items (Lunch, Movie, Toy) represent $1 - \frac{1}{4} = \frac{3}{4}$ of the total pie chart.

3. Calculate the total amount spent on the remaining items

Total spent on Lunch, Movie, and Toy = $\char36{}10 + \char36{}12 + \char36{}38 = \char36{}60$.

4. Calculate the amount spent on the book

Since $\frac{3}{4}$ of the total is $\char36{}60$, $\frac{1}{4}$ of the total (the book) is $\char36{}60 \div 3 = \char36{}20$.

1. Find the total amount spent on the items other than the book.

$\char36{}10 + \char36{}12 + \char36{}38 = \char36{}60$

2. Determine the total amount of money Michael had.

The 'Book' sector has a right angle ($90^\circ$), which is $\frac{90}{360} = \frac{1}{4}$ of the pie chart. The remaining items represent $1 - \frac{1}{4} = \frac{3}{4}$ of the total money.
Total money = $\char36{}60 \div \frac{3}{4} = \char36{}80$

3. Calculate the percentage of the total money spent on lunch.

$\frac{10}{80} \times 100\% = 12.5\%$