This Week From Bedtime Math: A Sundae for Taco Tuesday

How many scoops of ice cream can you fit in a taco? Wait, why is ice cream going inside a taco? Find out in today&s challenge from Bedtime Math.
By Laura Overdeck
Oct 21, 2014



Oct 21, 2014

What is Bedtime Math? A message from Laura: Bedtime Math is a pretty simple idea: We all know we should read to our kids at night, but what about math? My husband and I have done fun, mischief-loaded math problems with our kids at night for years, and when at age 2 our third child started hollering for his own math problem, we realized we were onto something:  In a world where so many people say, "Ewww, math!" we had created a household culture where kids don't just tolerate math, they actually seek it out. Now, every week, we'll be posting a new problem right here on Scholastic Parents!
If you've seen The LEGO Movie, you might know that Emmet and his friends love to celebrate Taco Tuesday — which, as you can guess, means eating tacos every Tuesday. Well, here we celebrated a Bedtime Math kid's birthday today with a Taco Tuesday birthday cake: a giant chocolate chip cookie folded into a taco and then stuffed with other foods to imitate real taco filling. There are vanilla and chocolate ice cream for chicken and beef, then yellow sprinkles for the cheese, shavings of frozen green frosting for the lettuce, chopped maraschino cherries for tomato, and whipped cream for sour cream.  We could have topped it with real lettuce and tomato, but this probably tasted better.

Hungry for more? See if your kids can come up with these Taco Tuesday-inspired math challenges:

Wee ones: If the giant taco cake has sprinkles, cherries, frosting, and whipped cream as toppings, how many toppings is that?

Little kids: If you're nibbling ice cream taco cake and you eat a spoonful of cherries, then sprinkles, then whipped cream, then back to cherries again to repeat, what's your 13th bite?  Bonus: What number is the next bite of that same ingredient?

Big kids: If the Taco Tuesday cake is 5 regular tacos long, 3 tacos wide, and 2 tacos thick, how many regular tacos could you fit inside this one? (Don't worry about edges lining up.)  Bonus: If the taco cake uses 14 times as much topping as a regular taco, how many teaspoons of sprinkles were needed if a real taco uses 4 teaspoons?

The sky's the limit: If the vanilla ice cream and chocolate ice cream add up to 16 scoops, the vanilla ice cream and whipped cream add up to 19 scoops, and the chocolate ice cream and whipped cream add up to 21 scoops, how many scoops of each ingredient were used?
Wee ones: 4 toppings.
Little kids: Cherries.  Bonus: The 16th bite, since it's every 3rd one.
Big kids: 30 tacos.  Bonus: 56 teaspoons.
The sky's the limit: There are 7 scoops of vanilla ice cream, 9 scoops of chocolate and 12 scoops of whipped cream.  You could solve this by trial and error, but algebra is smoother: if we have v, c and w, we can say:
v + c = 16 so v = 16 – c
v + w = 19
c + w = 21
Substituting the first equation for v into the second, we get
16 – c + w = 19
which simplifies to w – c = 3 or w = c + 3
Then substitute that for w in the last equation:
c + c + 3 = 21
2c = 18
c = 9
Then it follows that w = 12 (since it's 3 more) and v = 7 (since v and c total to 16).

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