Answer:
T=180minutes or 3 Hours
Explanation:
Given the teacher was able to grade 3/4 of the class papers in 2hours and 15 minutes. Let there be x number of children in the class. Now convert the time into one unit ie, minutes .
1 hour=60 minutes
2 hours=120 minutes.
total time taken by the teacher to grade 3/4 of the class papers is=120+15=135minutes.
Now
3/4 of the class papers graded in 135 minutes.
let the time taken to grade all the papers is T; then
![3/4x--->135](https://img.qammunity.org/2020/formulas/mathematics/high-school/nrdzvr93dy25juk9arqwfc69qx0triz367.png)
![x--->T](https://img.qammunity.org/2020/formulas/mathematics/high-school/77jbpo4bc0ye0kkbtuj1mwkp8i7z1dyq6b.png)
On cross multiplication we get
![135*x=T*(3x/4)](https://img.qammunity.org/2020/formulas/mathematics/high-school/yxdbuv89sa2ry7yxsnyqlum0myy7nosaju.png)
![T=135*4/3](https://img.qammunity.org/2020/formulas/mathematics/high-school/iqdtiw04tjsbtum3173zbi60xpt7e7dvzk.png)
minutes.
Therefore the total time taken by the teacher to grade all the papers in the class is 180 minutes or 3 Hours.