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For The Mathematically Inclined

Anil Saigal
07/23/2014

Problem #1
Thirteen per cent of the people in a certain town have unlisted phone numbers. You select three hundred names at random from the phone book. What is the expected number of people who will have unlisted numbers?

Problem #2
 A seaside resort along the Pacific Ocean is equipped with an electronic shark detection system which sounds an alarm on the average of 1 day out of 30. There are 10 times more false alarms than there are undetected sharks. We also know that only three out of four sharks are detected. Given the above information, what is the percentage of "peaceful" resort days if that term is defined as days unmarred by alarms or sharks?

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Please send your solutions to mr.asaigal@gmail.com.

Use Problem Solutions M-073114 as the subject line. Please include your full name in the text of the main message. Everyone with the right answer will be acknowledged in the next issue of Lokvani.

Please do not post your solution in Post Comments. No credit will be given for solutions not sent to anil@lokvani.com.

If you need clarification on any problem, please contact anil@lokvani.com.

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Solutions from 7/17/2014

PROBLEM #1
What is the missing number in Figure 1 on the right.

SOLUTION #1
16.


PROBLEM #2

What is the coefficient of a8b8 when you expand (a+b)16?

SOLUTION #2

9360.

Congratulations to Kishore Balsara, Saroj Gandhi, Saba Lateef and Eshana Rao, who were the winners of the last set of puzzles.



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