This Week From Bedtime Math: Digging a Hole to China

The miles and fun add up on the map in today&s challenge from Bedtime Math!
By Laura Overdeck
Sep 17, 2013

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This Week From Bedtime Math: Digging a Hole to China

Sep 17, 2013

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 we email parents a fun, lively math problem every day to do with their kids – and every week, we'll be posting a new problem right here on Scholastic Parents!

Sometimes when we're digging a deep hole in the backyard or in the sand at the beach, we kid about digging all the way through Earth and ending up in China. Well, digging a hole to China is hard for a few reasons. For one, you'd have to dig for almost 8,000 miles, because that's how wide the Earth is. Then there's the problem that the core of the Earth is solid iron and nickel at almost 10,000 Fahrenheit!

Even if you could take the heat, would you end up in China? Only if you happen to be exactly opposite there. If you're in the United States, you'll end up in the Indian Ocean, west of Australia. If you're in England, you'll end up in the South Pacific near New Zealand. And what if you're in China? You'll dig your way to Chile or Argentina, in South America.

Now that you've got your bearings, see if your children can dig through these challenges and come up with the right answers.

Wee ones: If you dig a 5-foot hole, take a break, then dig another 2 feet, how far have you dug?

Little kids: If you're digging in the sand and when you dig 10 feet, a foot of sand slides back in, now how deep is your hole?  Bonus: What if you try to dig 20 feet and it happens twice – how deep will your hole end up?

Big kids: The Earth is about 7,900 miles wide at the equator. If you dig for 3,000 miles, how many miles do you have left to go?  Bonus: How far are you from the center of the Earth?

Answers:
Wee ones: 7 feet.
Little kids: 9 feet.  Bonus: 18 feet.
Big kids: 4,900 more miles.  Bonus: The halfway mark is at about 3,950, so you have about 950 miles to go.

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