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Interview Question

Interview Redmond, WA

You are on a desert island, and all you have is a pair of

  dice. You know that a plane flies over the island on the 30th day of the month. Using the dice, how can you make a calendar that always tells you the day of the month?

Interview Answer

9 Answers


I don't remember the answer, but I didn't get it right. I figured it out later, and emailed the answer to the hiring manager.

Interview Candidate on Oct 30, 2013

Using the dice you can count to a maximum of 66 combined. When the plane flies by on the 1st month's 30th day, each day after that at the same approximate time in the day you can increase the value of the dice by 1. For example plain flies by on 30th day of 1st month. the next day you wake up and assuming plane flew by at dawn you place the side with the 1 facing up. Each dawn after that you increase to 2, 3, 4, 5, 6-- after six you would use both die, and make some indication to your self saying that 1+6= 7, 2+6=8... and so on after you reach the 4+6=10th day it would be easier to use the die to show "1""1"-> 11th day, etc. That way eventually, you can make a calendar that tells you the day of the month.

Rikesh Thapa on Oct 31, 2013

Using two digits in "base 6" you can count up to 35. Typically base 6 would use digits 0 to 5, but in this case you can adjust and use 1 through 6.

Brad Rawlins on Nov 10, 2013

@Rikesh: How will you indicate 17, 18, 19, 20, 27, 28, 29, 30. Here is what i think... D D 6*0+1=1 6*0+2=2 6*0+3=3 .. 6*0+6=6 6*1+1=7 6*1+2=8 .. 6*1+6=12 6*2+1=13 6*2+2=14 .. 6*2+6=18 6*3+1=19 6*3+2=20

Anonymous on Nov 13, 2013

Basically 2 dice has 6 sides so for Dice 1: mark 0 1 2 4 6 8 Dice 2: mark 1 2 3 5 7 9 And those two can make up all days of the month Or you can map 1-6 with those numbers for each dice

Anonymous on Nov 20, 2013

Rikesh's answer is not correct. cuz 1+6= 7. But with his implementation, you would use 1, 6 to represent 16th also. You can argue that you could use 6,1 to represent the 16th. However, I think MS wants the more "geek" way of the solution, which is one I upvoted the base 6 solution.

Anonymous on Dec 3, 2013

How about... Dice 1: each pip equals 1 day: 1 pip =1 day, 2 pips = 2 days, etc. Dice 2 each pip equals 5 days: 1 pip = 5 days, 2 pips = 10 days 3 pips = 15 days etc. Die 2 is always to the left of Die 1. For days less than or equal to 5 use 1 die. When counting a day that is a multiple of 5 (days 5,10,15 etc.) count day by putting Die to 5 pips and Die 2 to the remaining number of days.

Jim Beam on Jan 29, 2014

You are on Desert.. ! Why don't write the count down/up number on it. and cover using the dice ? Just a Approach keeping basis of PMO PM: Analytical thinking, – it’s thinking about the parts or elements of a situation. PMO: Synthetical thinking – it’s thinking about how those parts or elements work together.

Balaji on Jan 19, 2015

Given a Tea Powder, Milk, Gas Stove and two match stick to prepare Tea in less than 60seconds. Approach: Using the two match stick keeping crossed at Right angles and done "T" Its about "what can be done to achieve goal" not "what is given to achieve the goal"

Balaji M on Jan 19, 2015

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