Imagine an HIV test that is 95% accurate (false positive rate of 5%) and around 2% of the tested population is infected with HIV. What is the probability that you actually have HIV when your test comes back positive?
Silver tears falling down, Nature’s clear imposter, Sparkling, shining like a gown, Adorn an elephant or horse, Silver, PVC or even lead, Bringing cheer to all around, For such a simple thread.
Tinsel emulates icicles, which are like tears and are clear in nature. Tinsel sparkles and shines, and is used to adorn elephants and horses in India. Tinsel is made from silver, PVC and was once made from lead. Tinsel brings back fond memories to many (including myself) and represents far more than a simple metallic thread would normally warrant.
Last winter I found myself locked out of my house because I couldn’t remember the 5-digit code to open the garage door. I used the following facts to get inside.
1. The second and third digits add up to 9. 2. The first digit is equal to the second digit cubed. 3. The sum of the third and fifth digits is the smallest number with exactly five divisors. 4. The fourth digit is equal to 6 times the second-to-last digit. 5. None of the digits repeat.
If we label each digit a, b, c, d and e, we get the following equations. 1. b + c = 9 2. a = b3 3. c + e = 16 (since 16 is the smallest number with five divisors – 1, 2, 4, 8 and 16). 4. d = 6 * d (The fourth and second-to-last digits are the same number, meaning d must be zero to satisfy the equation) 5. b must be zero, one or two (b can’t be three because that makes a=27, which isn’t a single digit). Zero and one result in duplicate digits (00907 and 11808 respectively) so the only remaining value for b is 2, giving us 82709 and warmth.
1. How do you put a giraffe into a refrigerator? 2. How do you put an elephant into a refrigerator? 3. The Lion King is hosting an animal conference. All the animals attend except one. Which animal doesn’t attend? 4. There is a river you must cross but it is used by crocodiles and you don’t have a boat. How can you cross safely?
1. Open the refrigerator, put the giraffe in and close the door. It’s not complicated. 2. Open the refrigerator, take out the giraffe, then put in the elephant and close the door. 3. The elephant. He’s still in the refrigerator. After all, you just put him there. 4. Jump into the river and swim across. The crocodiles are at the Lion King’s animal meeting. I admit, this is not a typical brain teaser, but it amused me.