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December 19, 2014

December 19, 2014

Posted by **Shawna Lynn** on Monday, April 29, 2013 at 2:33pm.

Determine the digits of R from these clues.

The first digit is the answer when the third digit is divided by 2.

The second and third digits add to 7.

The second digit minus the first digit is 1.

R is a three-digit number: ____

I have never understood how to do this.

- Math -
**Steve**, Monday, April 29, 2013 at 2:50pmCall the digits a,b,c left-to-right

a = c/2

b+c = 7

b-a = 1

we see that c=2a, so

b+2a=7

b-a=1

subtract to get

3a=6

a=2

Thus c=4 and b=3

R=234

Or, just working with the specs,

c must be even, since it can be divided by 2. So, R is one of the forms

1x2

2x4

3x6

4x8

Since the last two add to 7, R must be

152

234

316

Since 2nd-1st=1,

R=234

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