In deference to the good sports in the readership who enjoy participating in the quizzes I present from time to time, but don't like ones with much math, please consider the following Birthday Sum Quiz.

I found the quiz on Readers who prefer to use logic (with just a modicum of arithmetic) will find this one enjoyable. Please let me know how you work the problem. I will post all correct answers or alternatively will send the solution privately to anyone who requests it if no one figures it out.

the National Museum Of Mathematics website (www.MoMath.org) after it appeared in the WSJ.

Birthday Sum Quiz

If you add up the two-digit year that somebody was born, the number of the month of their birthday from 1 to 12, and the day of the month of their birthday, we'll call that their "birthday sum." For example, somebody born in 1968 on Feb. 18 would have a birthday sum of 68 + 2 + 18 = 88.

What is the largest possible difference between birthday sums of people born on consecutive days?

Here is my solution.

ReplyDeleteThe largest number for a century is 99. The largest number for a month is 12, and the largest number of days in a month is 31.

99+12+31=142.

The consecutive birthday sum equals 00 for the year, 1 for birth day and 1 for the birth month.

00+1+1=2.

The difference equals 140.

Congrats - you hit this nail right on the head.

DeleteAfter about 10 seconds (+/-) here is my answer:

ReplyDeleteThe highest would be Dec. 31, 1999 (99+12+31=142) and Jan. 1, 2000 (00+1+1=2)

12/31/any year & 1/1/(any year + 1) = a difference of 40 .

ReplyDeleteLooks like this relationship holds up for all but the right answer. Look for that exception.

DeleteDoug - 12/31/99 and 1/01/00 with a difference of 140.

DeleteThis seems way too easy......140.

ReplyDelete140?

ReplyDeleteAsked several of my former students and the consensus is 140! They did it mentally - shame on me! Math is not my forte and I'm not willing to sic my mind on what is not that important to me. GULP!

ReplyDeleteIt is 41.

ReplyDeleteYou have the right idea - but think Y2K for the exception that is the answer.

DeleteI also came up with 140, actually very easy starting with year 2000 for lowest.

ReplyDelete