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Strange-But-True Mathematical brain teasers
Posted on 10/1/16 at 12:49 pm
Posted on 10/1/16 at 12:49 pm
Ran this thread last year and had fun with it. Thought it deserved another round. Algebra, Geometry, and Physics are also welcome. Here's my brain teaser.
Assumptions:
1. You have a smooth sphere as big as the Earth (25,000 miles in circumference at the equator).
2. You have 2 pieces of string. String 1 is 25,000 miles long and wraps around the sphere at the equator, touching the surface all the way. String 2 is also all the way around at the equator, except String 2 sits 1 foot off the surface all the way around.
Question: What is the difference in length between String 1 and String 2?
Assumptions:
1. You have a smooth sphere as big as the Earth (25,000 miles in circumference at the equator).
2. You have 2 pieces of string. String 1 is 25,000 miles long and wraps around the sphere at the equator, touching the surface all the way. String 2 is also all the way around at the equator, except String 2 sits 1 foot off the surface all the way around.
Question: What is the difference in length between String 1 and String 2?
25
Posted on 10/1/16 at 12:52 pm to tigerpawl
String 2 is twice as long?
Posted on 10/1/16 at 12:53 pm to tigerpawl
288
Posted on 10/1/16 at 12:54 pm to LordSnow
String 2 has two meters of added length
This post was edited on 10/1/16 at 12:58 pm
Posted on 10/1/16 at 12:54 pm to tigerpawl
String 2 > String 1
That's all I got.
That's all I got.
Posted on 10/1/16 at 12:55 pm to tigerpawl
But does 4+5=9?
Posted on 10/1/16 at 12:55 pm to tigerpawl
After some quick computing, the rope would only need to be 6.28 feet longer
Posted on 10/1/16 at 12:55 pm to FunroePete
25006
Sphere:
C=2pir
25000= 2(3.14)r
r=3980 and change
3980+1 = new radius
3981(2)3.14= 25006.28
25006.28-25000=6.28
Sphere:
C=2pir
25000= 2(3.14)r
r=3980 and change
3980+1 = new radius
3981(2)3.14= 25006.28
25006.28-25000=6.28
This post was edited on 10/1/16 at 12:59 pm
Posted on 10/1/16 at 12:56 pm to tigerpawl
6.28 ft
Posted on 10/1/16 at 12:56 pm to saint tiger225
Here's the cryptic answer: Cryptic Answer
This post was edited on 10/1/16 at 2:00 pm
Posted on 10/1/16 at 12:56 pm to tigerpawl
three fiddy
Posted on 10/1/16 at 12:56 pm to tigerpawl
quote:
What is the difference in length between String 1 and String 2?
String 1 was made in Japan, string 2 was made in China.
This post was edited on 10/1/16 at 12:57 pm
Posted on 10/1/16 at 12:57 pm to tigerpawl
Difference = 0.00118999722 miles
This post was edited on 10/1/16 at 12:58 pm
Posted on 10/1/16 at 1:01 pm to Bmath
Congrats to "Spilled Milk", "East Coast Band" and "Bmath". 
Brain Teaser #2....
Assumptions:
1. You have a smooth sphere as big as a basketball (30 inches in circumference).
2. You have 2 pieces of string. String 1 is 30 inches long and wraps around the sphere at the equator, touching the surface all the way. String 2 is also all the way around at the equator, except String 2 sits 1 foot off the surface all the way around.
Question: What is the difference in length between String 1 and String 2?
***Spilled Milk, East Coast Band and Bmath CANNOT PLAY!***
Brain Teaser #2....
Assumptions:
1. You have a smooth sphere as big as a basketball (30 inches in circumference).
2. You have 2 pieces of string. String 1 is 30 inches long and wraps around the sphere at the equator, touching the surface all the way. String 2 is also all the way around at the equator, except String 2 sits 1 foot off the surface all the way around.
Question: What is the difference in length between String 1 and String 2?
***Spilled Milk, East Coast Band and Bmath CANNOT PLAY!***
This post was edited on 10/1/16 at 6:21 pm
Posted on 10/1/16 at 1:05 pm to Boss
so your new radius is 3980 miles + 1 foot?
Posted on 10/1/16 at 1:07 pm to Gevans17
quote:Read the question.
so your new radius is 3980 miles + 1 foot?
Posted on 10/1/16 at 1:08 pm to Boss
6.28ft more in length
Posted on 10/1/16 at 1:09 pm to Bmath
quote:
Difference = 0.00118999722 miles
Correct
Posted on 10/1/16 at 1:09 pm to BoogerEater
quote:Also correct. Also applies to ping pong balls and the planet Jupiter.
6.28ft more in length
This post was edited on 10/1/16 at 1:17 pm
Posted on 10/1/16 at 1:12 pm to Boss
quote:
3980+1 = new radius
Wouldn't your new radius be +2?
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