Answer:
15 seconds
Explanation:
Simply assume that total length to be covered be 'L'.
Now ,
of total length L is covered in time
.
We know distance traveled =speed×time
Let Object's velocity be V
Using this
![(L)/(20)=V×time](https://img.qammunity.org/2020/formulas/mathematics/middle-school/berjn6xfhkzn81bxg6di8hkcolgsasdyq8.png)
![(L)/(20)=V*(3)/(4)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3wfrrmveadzjj8ficzaos2kironehuqhgi.png)
Thus, velocity in terms of total length is
![V=(L)/(15)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/9f3yl4u36r9tmk5z09ko4sj6nwkzuzsqk6.png)
Now,
To cover total length L time needed is
![time =(distance)/(speed)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/aiebc2qtkeuc46qsoz17oh8tvenfcxjt23.png)
![time=(L)/((L)/(15) )](https://img.qammunity.org/2020/formulas/mathematics/middle-school/kbd449buxvy5zv1anvzhj49csrug5413wv.png)
Time taken =15 seconds