Math Is Fun Forum

gmleiva68

Guest

Number puzzles

Take the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 and insert numerical operations between the numerals so that the result will equal 100. The order of the digits must stay the same. What are some possible solutions to this puzzle? After you solve the problem, try solving it by inserting only addition and subtraction operations between the numerals. Create three other puzzles like the above puzzle. Please, do not forget the following things:

Explanation of solutions

Explanation of approach

Use of models

Development of similar problems (3)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Number puzzles

Hi gmleiva68;

Here is one way:

Can you find another?

Here is one that just uses + and -

Can you find one like I did?

Try this one yourself.

As a suggestion for other problems how about going backwards, 9 to 1 to get 100?

For the thought processes I afraid that you have to do a little bit of your own work too. I suggest you do one of each type on your own then you will be well equipped to explain it to your teacher.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

gmleiva68

Guest

Re: Number puzzles

Hi bobbym:

Thanks for your answer.

As a suggestion for other problems how about going backwards, 9 to 1 to get 100?

Answer:

(9x8)+7+6+5+4+3+2+1=100

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Number puzzles

Hi;

That is very clever and obviously correct.

Here is a nice page that will give you everything you want.

http://www.worldofnumbers.com/ninedig1.htm

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.