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My adventures trying not to flunk math in high school may explain why a new book caught my eye recently. It’s called Math Hacks: Cool Tips + Less Stress = Better Marks, and it’s full of bite-size practical tips for young students and their parents on how to be better at math.

I asked the author, Vanessa Vakharia, if she might have some math hacks to help readers of this newsletter. “Here are my five favourite math hacks to help you essentially monetize your everyday decisions,” she wrote back. “Yes, that’s a thing.”

1. Size Matters (Unit Size, That Is)

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If you’re at the grocery store and that 1L bottle of coconut water is $10 and the 250mL bottle is on sale for $2.75 each, which one is the better deal? When both broken down into milliliters, you’ll discover that 1L = 1,000mL, so you’re paying $10 for 1,000mL. That’s $10/1,000 = $0.01 per mL. The smaller bottles are $2.75 for 250mL. That’s $2.75/250 = $0.011 per mL. Cha-CHING! In this case it’s cheaper to get the bigger bottle.

2. Bigger Isn’t Always Better

Just because something is on sale, doesn’t mean you should buy it. If you’re going to watch perishable items grow mouldy and cosmetics collect dust, just say no.

3. Know Your Worth

To buy or not to buy that $180 pair of Timberlands…here’s a trick a friend taught me. She places the value of everyday items she purchases at $1 per use. So, in this case, $180 = 180 uses. Are you going to wear those Timbs 180 times? Well then, $1 for each time you sludge through the snow doesn’t seem so bad!

4. Sales Tax = Money Out of Your Pocket

The total amount paid for an item is the total amount that you kiss bye-bye from your bank account. Grab your phone and tack on that 13 per cent by multiplying the price on the tag by 1.13 to get a reality check on what you’re actually spending.

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5. The Magical Rule of 72

Ever wonder where that 3 per cent GIC is going to get you? If you divide 72 by your rate of return, the answer tells you how many years it will take your initial investment to double. So say you take $1,000 and throw it in a 3 per cent GIC. In 72/3 years (read: 24 years), you’ll have $2,000!

Subscribe to Carrick on Money

Are you reading this newsletter on the web or did someone forward the e-mail version to you? If so, you can sign up for Carrick on Money here.

Rob’s personal finance reading list…

Step-by-step instructions for getting a better deal on cable TV and internet

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I like this – show people how to do something, don’t just tell them to do it. Here, we have instructions for getting a better deal from Telus and Shaw. The general principles apply to other providers as well.

This is the top regret people have about buying a home

The top regret is just what you’d think – the high cost of maintenance, repairs and other costs. This story is based on U.S. numbers, but every home owner will recognize the stress caused by having to come up with thousands of dollars to fix problems with plumbing, a roof, foundations, driveways and more.

How to return food to the grocery store

No, I’ve never done it. But it makes perfect sense to take unsatisfactory purchases back to the supermarket. If you decide to return something, consult this guide to return policies at major Canadian grocery chains.

Is our tax system sexist?

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A new report answers this question by saying that, of 45 federal tax deductions, credits, breaks and loopholes, only eight pay out more to women than men.

Today’s financial tool

The deadline for filing your income tax return in most cases is April 30. Use this calculator to estimate your tax owing for 2018. Here’s a 2019 tax calculator.

Ask Rob

Q: I’ve invested in mutual funds through an adviser for 30 years. I have done well, but exchange-traded funds interest me with their much lower management expense ratios (MERs). However, I’m not confident to do the investing on my own. What do you think of the ETFs now being offered by companies like Fidelity and Mackenzie?

A: Several mutual fund companies have jumped into the ETF business, but their products are too new for me to consider them for my annual ETF Buyer’s Guide. I’ll have more to report as these funds build a track record. A lot of readers are asking about switching from mutual funds to ETFs these days. This prompted me to do a video on mutual funds versus ETFs.

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Do you have a question for me? Send it my way. Sorry I can’t answer every one personally. Questions and answers are edited for length and clarity.

What I’ve been writing about

- Seniors getting into trouble tapping their home equity to generate retirement income

- These parents charge their millennial child rent. How should they invest the money? (for Globe Unlimited subscribers)

- Cars, houses, Facebook and stagnant incomes – why you’re so stressed about money (for Globe Unlimited subscribers)

More Carrick and money coverage For more money stories, follow me on Instagram and Twitter, and join the discussion on my Facebook page. Millennial readers, join our Gen Y Money Facebook group. Send us an e-mail to let us know what you think of my newsletter. Want to subscribe? Click here to sign up.

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