To help you pass the class? To help you seem smarter to your boss? To help you make your parents happy?
What if? This is the true power of Excel and all of the other spreadsheet programs. VisiCalc and Lotus 1-2-3 were the predecessors and they changed the world of presenting the What If idea. Prior to spreadsheet software, most of these calculations were done manually on ledger paper. Changing any one value to see how it affected the outcome required a healthy amount of erasers, calculator tape and time. Anyone old enough to recall that drudgery immediately understands the revolution of this software. But in the end...the power was in the ability to create information from raw data (a presentable idea) and cause change...in a fraction of the time.
Alas, Excel is merely a computerized tool...software created to make calculations more efficient. You can live without it for sure. But if you’re in the business of presenting ideas and creating change (and almost everyone is), it’s very likely a spreadsheet will make your life much, much easier. One more thing...it’s a common worldview that proficiency with a spreadsheet means you're smarter. And this is a powerful advantage in gaining acceptance of an idea and making change. People trust smart people and are more likely to listen to what they have to say.
Learn and use Excel to change the world. Learn the =sum function to pass the test.