Math for Grownups (28 page)

Many studies have shown that muscle burns more calories than fat. That idea boils down to an amazing weight-loss secret: If you’re more Popeye than Olive Oyl, you may be able to have extra dessert without the extra pounds. That’s because adding muscle mass boosts metabolism.

Building muscle offers other health benefits, too. Creaky joints? Muscle strength can help. Worried about osteoporosis? Adding muscle can increase bone density and lower your risk of fractures. Want to reduce your chance of a heart attack? When the body is leaner, your ticker is healthier. (It is a muscle, after all!)

With all of these rewards, who wouldn’t want to add strength training to their workout?

Whether you’re using free weights or a machine at the gym, there are two parts of strength training: the amount of weight you’re lifting and the number of times you repeat each exercise. (Hey! Those are numbers!)

A little bit of math can keep you from being a complete dumbbell at the gym. Take a look at this sample bench-pressing workout.

This chart looks a little like Ahnold’s German, so let’s break it down. A
set
is the number of times you lift a particular weight in a row. So each time you work out, you’ll do three sets. And as the weeks progress, you’ll change the number of times you lift that weight.

But how do you know how much weight you should be lifting for each exercise? The chart tells you that, too. But you need some additional information. That’s where something called the “1 rep max” comes in.

Also called 1RM, the 1 rep max is the most you can lift in 1 repetition. The percents in the chart refer to the percent of 1RM that you’ll lift for each set. So if you can lift 10 pounds as your 1RM, then 85% of that would be 8½ pounds.

As the weeks progress, the sets get more and more intense. You start out lifting 65% of your 1RM, and by the third week, you’re lifting 95% of your 1RM. (The last week is a resting week.)

So how do you find your 1RM? You choose a weight to lift for a particular exercise. Do the exercise with that weight. Count how many times you can lift the weight before your muscles are completely fatigued. Then use the Brzycki formula to find your 1RM. Here it is:

Let’s try it out. Matt can bench-press 100 pounds five times before his muscles are fatigued. What is his 1RM?

So Matt’s 1RM is 112.5 pounds.

His personal trainer has suggested that he follow this workout in the first week:

How much will he need to lift for each set?

Once Matt finishes the first month of his workout, he’ll need to find his 1RM again. He has gotten stronger, after all! Once he has a new 1RM, he’ll adjust his workout, this time adding more weight.

Matt has to add weights to the barbell to make it weigh the right amount: 73 pounds, 84 pounds, and so on. But the bar itself weighs something. If he slides 73 pounds of weights onto it, he’ll have a barbell that weighs a lot more than 73 pounds. He has to consider how much the bar weighs.

A standard Olympic bar weighs 45 pounds, so how much will Matt need to add to get to 73 pounds?

73
–
45
=
28 pounds

Here’s another question to consider: Should Matt add 28 pounds to each side of the bar? Nope. He needs to put half of the 28 pounds on one side of the bar and the other half on the other side.

28
/
2
=
14 pounds on each side of the bar

The weights Matt is using are available in 50-, 25-, 10-, 5- and 1-pound sizes. What are his options for each side of the bar?

One 10-pound weight and four 1-pound weights

or

Two 5-pound weights and four 1-pound weights

What if Matt doesn’t have any 1-pound weights? In that case, he should probably choose one 10-pound weight and one 5-pound weight or three 5-pound weights. How much more will Matt be lifting if he has no 1-pound weights? Just 2 pounds.

On the Road: When Will You Get There and How Much Will You Spend?

Sometimes it’s just good to get away—to leave the daily grind, stretch out on a beach somewhere, and forget your everyday life.

Just remember, math never takes a holiday.

Whether you’re trekking for pleasure or profit, planning your trip will probably require a little addition, subtraction, multiplication and division. But like most everyday math, these calculations don’t have to ruin your good time.

ETD and ETA—they’re such a big deal that everyone knows their acronyms. Your estimated time of departure and estimated time of arrival can make or break a business trip, family vacation, or romantic getaway.

But with time zones and the pesky way that time is measured, figuring out when you’ll arrive—or when you’ll depart—can be tricky.

Quinton is so ready for spring break. And who wouldn’t be happier lying on the beaches of Mexico than trudging the rainy streets of Boston? He’s booked the entire week in Cancun and is meeting up with some old friends from high school to boot.

And that’s exactly why Leroy left him a message yesterday. Quinton’s old buddy is flying in a day earlier than Quinton and has agreed to pick him up from the airport. He just needs to know what time to be there.

The problem is that Quinton doesn’t have his airline ticket printed, and he’s not near his computer so he can look up the time. He does know these things:

1. He’s leaving Boston at 1:30
   P.M.
   
2. He has a 90-minute layover in Chicago.
   
3. The first leg of his flight is 45 minutes long.
   
4. The second leg of his flight is 5 hours long.
   
5. Cancun is 1 hour behind Boston.
   

Quinton needs to call Leroy back with his arrival time, but first he has to figure out how long he’ll be flying and sitting around the Chicago airport—and he also needs to figure in the 1-hour time difference.

He starts by finding the amount of time he’ll be flying. For that, he simply needs to add the flight times:

45 minutes
+
5 hours
=
5 hours and 45 minutes

But he’s got that 90-minute layover to consider too, so he adds that.

5 hours and 45 minutes
+
90 minutes

Quinton has a few choices now. He could convert everything to minutes and then add. Or he could convert to hours. He thinks a moment before deciding.

If he converts to minutes, he’ll have to add some large numbers, and then he’ll have to convert back to hours to figure out what time he’ll arrive in Mexico. On the other hand, he could convert the minutes to hours and deal with a few fractions instead. Even though fractions look messier, they’re sometimes easier to deal with in his head.

Quinton opts for the fractions.

45 minutes is ¾ hour, so

5 hours and 45 minutes is 5¾ hours

and

an additional 90 minutes is 1½ hours

Now the addition is pretty simple:

5¾
+
1½

To handle this without much fanfare, Quinton breaks up the 5¾ into two parts: 5¼ and ½.

5¼
+
½
+
1½

5¼
+
2

7¼

So, Quinton will be traveling for 7 hours and 15 minutes (including his layover). Because he leaves at 1:30
P.M.
, he’ll arrive in Cancun at 8:45
P.M.

Well, not quite. That’s still Boston time, so Quinton needs to subtract an hour: otherwise, Leroy will be there an hour behind schedule.

He calls up his good buddy to tell him the news: He’ll be there at 7:45
P.M.
Just in time for happy hour. (It’s always happy hour in Cancun.)