CRANIUM CHALLENGE
NOVEMBER CHALLENGE “ Light bulb break drop ”
You have two light bulbs in a 100-story building . You want to find out what floor the bulb will break on , using the least number of drops .
Please send you answers to Thomas Selling via e-mail : thomasselling @ me . com Correct responses will be recognized in the future issues of the New Hampshire Civil Engineer .
OCTOBER SOLUTION
The answer to this math riddle is 21 . You probably just guessed to answer this math riddle , which is fine , but you can also work it out algebraically . The two-digit number ab stands for 10a + b since the first digit represents tens and the second represents units . If 10a + b = 7 ( a + b ), then 10a + b = 7a + 7b , and so 3a = 6b , or , more simply , a = 2b . That is , the second digit must be twice the first .
CORRECT ANSWERS PROVIDED BY :
Kevin Garvey , PE , Wright-Pierce William Lambert , PE , NHDOT Jeff Beneay , PE , SFC Engineering Partnership , Inc . Kirk L . Stenersen , PE , Higher Design , PLLC Mike Dugan , GPI
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