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Post a mathematical riddle.

  • Come up with an algorithm that counts down from a number but does not employ the use of a minus sign or any form of subtraction. There are several solutions to this problem.


  • How can you add eight 8's to get the number 1,000? (only use addition)

(TQU: 888+88+8+8+8 = 1,000)

  • Start with six vertical lines. Then add 5 more lines to make nine.
  • Find the pattern: 8, 11, 15, 5, 4, 19, 7, 6, 3, 22, 2
  • If an analog clock shows the time 4:30, what is the angle between the hour and minute hand?

(BD: Angle covered by each hour = 360deg/12hour = 30 degrees/hour. At 4:30, hour hand is halfway between 4 and 5, and minute is at 6--so, 30 deg between 5 and 6, and an additional 15 between 4.5 and 5 = 45 degrees.)

Alumni Liaison

Ph.D. on Applied Mathematics in Aug 2007. Involved on applications of image super-resolution to electron microscopy

Francisco Blanco-Silva