So March 20 is pretty special, and not just because it’s the 79th day of the year. In most years March 20 is the start of spring, also called the vernal equinox. Equinox comes from the Latin words for “equal night,” because on this day Earth is tilted perfectly so every spot on the planet has 12 hours of both day and night. Because of that perfect tilt, people try to balance an egg on end at the exact moment of the equinox. Does that actually work? It does – because you can balance an egg any time! And, as noted in this week’s family activity on our Add It Up blog, eggs are also incredibly strong. While they break easily if they fall sideways onto the floor, they hold up surprisingly well when you press in on them. Take a couple of small plastic cups, stack your egg between them as shown here, and try balancing lots of heavy objects…you’ll find your egg can stand up to a lot.
Wee ones: How many eggs are in a “dozen”? If you have a 1-dozen egg carton, count to find out!
Little kids: If you stack a 10-pound book and your 10-pound cat on top of an egg, how many pounds is your egg holding? Bonus: If your egg can hold 40 pounds without cracking, how many more books (or cats) that size could you stack on it?
Big kids: Today’s equinox was at 12:57 pm Eastern time. If you started trying to balance your egg at 12:39 pm, how many minutes did you have until the equinox? Bonus: If you got the egg to balance right on the equinox and it stood for an hour and 15 minutes, when did the egg finally tip over?
The sky’s the limit: If you have 2 dozen eggs, and you balance half as many as you pressure-test and you pressure-test 1 more than you use to make pancakes, how many eggs do you balance?
Answers:
Wee ones: A dozen equals 12 eggs.
Little kids: 20 pounds. Bonus: 2 more books (or cats).
Big kids: 18 minutes. Bonus: 2:12 pm.
The sky’s the limit: 2 dozen eggs means you start with 24 total. If you balance b eggs, test t eggs and make pancakes with p eggs, we have enough equations to solve all three:
b + p + t = 24
b = 1/2 t , and p = t – 1
So
1/2 t + (t-1) + t = 24
Multiply the whole thing by 2 to clear the fraction:
t + 2t – 2 + 2t = 48
…then simplify.
5t – 2 = 48
5t = 50, so t = 10
Does that work? You test 10 eggs, use 9 to make pancakes (1 less than you tested), and balance 5 (half of what you tested)…and that does add up to 24 eggs.
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