Hint: Design a calculator. Standard, scientific, or speciality calculator for something such as a mortgage? Is it for phone, a tablet, a web app? (It’s up to you!)
I always find it tiresome having to do sums on the calculator and remember the answers whilst I do the next sums. So I have designed a calculator with a ‘Store’ button. You can store up to four sums. Hold whichever ‘Store’ button you like down after completing a sum and it will remember the whole thing for you. Never again worry about who’s paying for what at a restaurant or what you owe someone if they owe you money too.