Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Anna can read 1 page in 1 minute. Carole can read as fast as Anna but at half the speed of Brianna. How long does it take Brianna to read a 100-page book?

### Response:
If Anna can read 1 page in 1 minute, then her speed is 1/1 = <<1/1=1>>1 page per min
If Carole can read at Anna's same speed then her speed is also 1 page per min
If Carole is only half the speed of Brianna, then that means for every 1 page Carole reads, it takes Brianna 1/2 = 2 pages
If it takes Brianna 2 pages to match the speed of Carole, then her speed is 2/1 = <<2/1=2>>2 pages per min
If a book is 100 pages long and Brianna can read 2 pages per min then it will take her 100/2 = <<100/2=50>>50 minutes to read the book
#### 50