Which investment would you take, one that costs a dollar and returns 100, or one that costs 20 and returns 25? This problem isn't a head scratcher. We all instantly recognize that the 100X payoff is the better bet. But when it comes to time, somehow deciding how to spend this limited resource isn't always as clear-cut.

We spend hours emptying our inbox to little effect, or waste whole afternoons checking social media or browsing the web. Meanwhile, there are a few activities out there that are the temporal equivalent of that awesome 100X investment, activities that if you spend mere minutes on them early in the day, will pay you back with vastly more energy and productivity later on.

What are they? Quora users recently converged on a handful of sure bets when a curious poster wanted to know, "What can I do in 5 minutes in the morning to make my whole day better?" (Hat tip to Business Insider for the pointer to the thread.). Here are the answers that came up again and again, as well as links to the scientific reasoning behind the power this these simple morning routines.

1. Writing

Many people think of writing as something teachers or work forces them to do, but there's a huge pile of science showing that taking a few moments to write out your thoughts is a phenomenal way to boost your mental health. All it takes is a five minutes daily thought dump.

"Use the Five Minute Journal every morning. You'll feel more positive and happier when you use it. Your whole day will be better as a result," suggests entrepreneur Chris Remus. "I actually used it for 6 months, stopped and came back to using it. That was over five years ago and I haven't looked back since."

Or combine two powerful science-backed happiness boosters into one and opt for a gratitude journal instead. That's what another entrepreneur respondent, Nela Canovic, advises: "Write down 3 things you are grateful for today. Think about what you already have in your life. Don't focus only on material things (such as a car or a computer), but rather think in more simple or basic terms, such as having."

2. Meditation

Meditation might sound like a difficult undertaking only tackled by monks or tech executives with Herculean levels of self control and a lot more household help than you have, but experts insist that you can get the benefits of mindfulness meditation in just a few minutes a day. And what an array of benefits you can expect. Meditation has been shown to do everything from increasing focus to lowering blood pressure and even helping raise profits (Yes, really).

Quora users agree wholeheartedly with this chorus of meditation boosters. "Sitting for 5 minutes to detach from the thoughts of your mind will have a profound impact on your day," insists founder Ariel Banayan. "You'll understand your own negativity better. You'll have just a little bit more freedom from your thoughts so that you can focus on what has to be done during the day without excess thinking."

Engineer Raviteja Chirala assures readers that getting started is easier than you imagine. "Don't worry about reading about how to do and all. It's as simple as closing your eyes for five minutes without any distraction and focus on your breath and nothing else," he writes.

3. Exercise

Much like meditation, the scientific case for the benefits of exercise is open and shut. And just like with meditation, the range of potential positives from even a little physical exertion will probably surprise you. Exercise won't just make you fitter and healthier, it'll make you smarter, happier, and less stressed too, research shows.

With an upside like that, how could it not be worth setting your alarm a few minutes earlier, argue a number of Quora respondents. "Morning exercise does not just wake up your body, it gives you a dose of adrenaline to clear your mind and help you to focus," claims product designer Minh Killy Le. "Working out in the morning also results in numerous benefits such as upbeat mood, positive thinking, more healthy metabolism, etc." And you only need five minutes to feel these effects, he insists.

"Try any intense workout in the morning," agrees Chirala. "It can be a HIIT or any regular workout that can push your boundaries. For example running, crunches, push-ups, squats. Whatever you're comfortable doing in your limits and yet not really comfortable. This excites your body and helps it to get on track for the rest of your day."