Can You Solve This Math Problem?
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I love stories about people who didn’t give up. Miles Levin is such a story. Stories of perseverance help to motivate us in all aspects of our life, including our financial lives. But how do we teach perseverance to our kids? That was my challenge this weekend when my son was trying to solve a difficult math problem.
Using the numbers 1 through 9 in order, construct a math problem that equals 100.
Simple enough, right? If you can add, subtract, multiply and divide, you can solve this problem. When the answer didn’t come easily to him, he wanted to give up. But through encouragement (ok, and some threats, too), he worked through the problem and solved it. I told him that life is a series of problems, just like this one. And at each step in life, you have a choice–give up or keep trying. And we answer that question every day, whether we realize it or not.
So can you solve the math problem? Leave a comment if you think you’ve got the answer. Oh, and here’s a hint: You can use parentheses to change the order of operation.
15 Comments, Comment or Ping
Rob
How about…
1+2+3+4+5+6+7+(8*9)
Sep 4th, 2007
DR
Rob, well done. What I like about this math problem is how simple the solution appears. There are other ways to solve the problem, by the way, so leave a comment if you have figured out these other alternatives.
Sep 5th, 2007
Al Brockman
I have three possible solutions - two from my son; one from my son-in-law. Here they are:
1.
100 = (1+2+3+4) x [(5-6) x 7 + 8 + 9]
2.
1-2*3-4+5*6+7+8*9 = 100. I like this because, though parentheses could be applied, you don’t need them if your order of operations is correct. I’m mucking around with something more creative (exponents are allowed, right?)
3.
I think I could come up with the simple ones with a C program (sigh - it was going to be a shell script, but C handles arrays better) — there are eight operands, and (presuming simple math plus exponents) five possibilities for each operand: + - * / ^, which means 5^8 combinations, or 390625. All you have to do is build a 390625 row array with eight columns, each row representing a possible combination. Then you run something that translates, say,
1 1 1 1 1 1 1 1 into 1-2-3-4-5-6-7-8-9, and evaluates whether that equals 100.
After that, it’s, as my high school geometry teacher would say, “just plug & chug”
Sep 5th, 2007
DR
Al, very, very nice. Now if I can just think up a great article with the title, “Just Plug & Chug.”
Sep 6th, 2007
Sara
One more (many possible variations):
* 9) = 100
1 + ((2 + 3 + 4 - 5 + 6 - 7 +
Sep 6th, 2007
Sara
obviously, that should be an 8 then ) — not a “cool face”
Sep 6th, 2007
DR
Sara, very nice. This “simple” math problem reminds me that there are often multiple solutions to the same problem or challenge. Money is the same way. There are definitely many wrong answers. But there are also several paths that each can get us to our goals.
Sep 6th, 2007
Linda
What is the future value, if the present value is $1 and the interest
rate is 2% annually after 7 years?
Mar 19th, 2008
Linda
what is the future value, if the present value is $5 and the
interest rate is 3% annually after 10 years?
Mar 19th, 2008
Linda
You have a savings account with $100 earning 4% annually. What
would the value of this account be after 30 years?
Mar 19th, 2008
DR
Linda, the answer will depend in part on the rate at which the interest compounds (daily, weekly, monthly, annually). But that said, my answer for this and your other questions is (in round numbers) $324.34, $6.72 and $1.15.
Mar 19th, 2008
Mike
Find the numbers
Use each of the digits 0-9 only once, to write five two digit numbers, which has the sum of 288
Apr 10th, 2008
Erica
You have been hired by a day care agency to fence in an are a to be used for a playground. You have been provided with 60 feet of fencing (in 4-foot sections) and a foot gate. How can you put up the fence so the children have the maximum amount of space in which to play?
May 7th, 2008
sabrina
i am receiving a $20 million which has to be divided among 270,000 people, so how much will we all receive?
Jun 19th, 2008
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