He read 1/5 of the book on Friday
Here, we want to get the fraction of the book read on a particular day
From the question, we are told that 4/5 was left and 1/4 of this was what he read
For convenience sake, let us have a specific number of pages for the book
Let the number of pages the book have be 200
He has 4/5 unread
The number of pages left to read will be;
![(4)/(5)*200\text{ = 160}](https://img.qammunity.org/2023/formulas/mathematics/college/4e8iek2dp3p7k3xn16ytx9h72d86pk2e18.png)
Now, he proceeded to read 1/4 of this
The number read will thus be;
![(1)/(4)*160\text{ = 40}](https://img.qammunity.org/2023/formulas/mathematics/college/u1xrd5dge6sdtt722lttbab6r1fmnh2n0o.png)
Now, we want to calculate the fraction of the book that corresponds to this
Mathematically, that would be;
![(40)/(200)\text{ = }(1)/(5)](https://img.qammunity.org/2023/formulas/mathematics/college/23ow8xyix2oz2s3mfdn2h3r2s6ti24gsou.png)