Paper LBO in 45 minutes: how do you even prep for this?

I've got a paper LBO coming up, 45 minutes, pen and paper only. I'm fine with LBOs in Excel, but by hand with a timer? How did you prep?

Did one last year. The maths is easy, it's the clock that gets you. Write every step so whoever grades it can follow, even if you mess up one number.

The order I use: entry EV = EBITDA x entry multiple, split into debt and equity (they usually give leverage, like 5x or 6x EBITDA). Project EBITDA to the exit year. FCF each year = EBITDA minus capex, interest, taxes and change in NWC, and all of it pays down debt. Exit EV = exit EBITDA x exit multiple, minus the debt left = equity at exit. MoM = exit equity / entry equity, then IRR from rules of thumb.

Quick example to check yourself. EBITDA 100, 10x entry so EV 1,000, debt 600, equity 400. EBITDA gets to 150 by year 5, exit at 10x = 1,500. Say 200 of debt is paid down from FCF, so 400 left. Exit equity 1,100, that's 2.75x in 5 years, roughly 22%.

Also practise without a calculator. I did about 8 the week before and was finishing in 25 minutes by the end. And don't forget interest in FCF: I forgot it on my first one and my IRR was way too high.

Update: did it today and finished with 5 minutes to spare. Nothing weird, almost exactly the structure above. Thanks everyone.