It took Rohan 45 mins to write half a page and there are ten pages. That means it would of taken 90 mins for 1 pages (45 times 2) since they are 10 pages you need to times that by 10
90 times 10 = 900 minutes You may need to confer that into hours so 900 divided by 60 (an hour) 900 divided 60= 15 hours/900 minutes