Math riddle

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(AB x 2) – 1 = BA

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Type: Question • Score: 0 • Views: 595 • Replies: 12

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@whimsical,

A=1 B=1
or
A=-1 B=-1

2 Replies

@fresco,

thanks

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@fresco,

Can there be a solution where A is not the same number as B? Or is that impossible?

1 Reply

@whimsical,

whimsical wrote:

Can there be a solution where A is not the same number as B? Or is that impossible?

A x B must equal 1. Using integers, A and B must be -1 or +1. However there is an infinite number of solutions, if fractions are allowed,

Code:

A=1/2   B=2   A=2      B=1/2

A=1/4   B=4   A=4      B=1/4

etc ad infinitum

all of this form:
A = N, B = 1/N
or
A = 1/N, B = N

1 Reply

@whimsical,

(AB x 2) – 1 = BA

2 x (10A + B) - 1 = 10B + A

20A + 2B -1 = 10B + A

19A = 8B + 1

B = 7, A = 3

2 Replies

@ekename,

ekename wrote:

B = 7, A = 3

so ((7x3) x 2) -1 = 7x3?

so 41 = 21?

1 Reply

@centrox,

Quote:

(AB x 2) – 1 = BA

When A and B represent single digit integers, AB and BA can be construed to be two digit numbers.

If A = 3 and B = 7 then

37 x 2 -1 = 73

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I was going by the conventional algebra representation I was taught in school, e.g.

https://images2.imgbox.com/9e/8f/odyD3SqP_o.jpg

Where "AB" means "A multiplied by B"

2 Replies

@centrox,

...as was I. But come to think about it there are 'riddles' using letters as place value digits. If I find one I'll post it.

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@centrox,

Thanks..

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@ekename,

Aha cool...

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@centrox,

....S E N D
+ M O R E
________
M O N E Y

I think these are called 'alphmetic riddlee'. I'm trying thie one noe.

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Math riddle

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