Radio Astronomy Systems Research Group

By moving only a single digit or sign, make the following equation valid.¹⁾ 62 - 63 = 1 Answer

There is a chef famous for his 9 minute boiled egg. Sadly, his 9 minute hourglass broke one morning. He looks around the kitchen and finds two hourglasses: one has 4 minutes worth of sand in it, the other has 7. Is there a way for the chef to measure 9 minutes using these two hourglasses? ²⁾

Answer

There were 2 Bedouins in the desert: one had 5 loaves of bread, the other had 3. Another Bedouin meets them and wishes to share a meal with them. He has money, but no bread. They split the bread evenly and sit down to eat. After the meal, the third Bedouin thanks them and leaves them with 8 gold coins. How can the two split the money fairly? ³⁾

Answer

“Semiprimes are highly useful in the area of cryptography and number theory, most notably in public key cryptography, where they are used by RSA and pseudorandom number generators such as Blum Blum Shub. These methods rely on the fact that finding two large primes and multiplying them together (resulting in a semiprime) is computationally simple, whereas finding the original factors appears to be difficult. In the RSA Factoring Challenge, RSA Security offered prizes for the factoring of specific large semiprimes and several prizes were awarded. The most recent such challenge closed in 2007.” (Semiprime on Wikipedia)

For a simple example, find the prime factorization of the semiprime number 391. ⁴⁾

answer

Draw this design without retracing lines, no overlapping lines and without lifting your pen. ⁵⁾

answer

Treating each line as a matchstick that can be picked up and moved, make the following equation equal to 4 by moving only a single stick. ⁶⁾

   | + || + ||| + ||||

answer

Gauss could famously add a large number of consecutive digits from a young age. For this question, sum all the digits of each number from 1 - 1 million. As a brief example, consider the numbers 1-10. ⁷⁾

  1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 1 + 0 = 46

answer