If you have to attempt 5 questions in 2.5 hours, you need to give 30 minutes to every question.
5 minutes for brainstorming, 5 minutes of outline and 20 minutes of writing.
Keep the writing according to the outline and then even if it's 3-4 pages the outline will serve the purpose. While the easy questions can be extended to 4-6 pages.
I myself can write 20-25 pages in 2.5 hours. Don't know about others. But keeping the answers precise and to the point is better than writing low quality stuff.