+ X X Y Y Z Z Z Y X
Let X , Y and Z be three distinct single digits satisfying the cryptogram above with X = 0 . Find the value of the three digit integer, X Y Z .
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My solution is not going to be very well formated but here is my solution. XYZ + XZY = YZX XYZ = 100X + 10Y + Z XZY = 100X + 10Z + Y YZX = 100Y + 10Z + X Simplifying produces 200X + 11Y + 11Z = 100Y + 10Z + X Bring all the terms to one side 199X + Z - 89Y I don't know if there is a way to directly figure it out from here but after placing numbers in the equation 199x4=796 X=4 Z=5 89x9=801 Y=9 Placing them back in the problem gives you: 459+495=954 the correct answer!
I am never good at cracking cryptograms so I did it this way:
We have,
X Y Z = 1 0 0 X + 1 0 Y + Z → ( 1 ) X Z Y = 1 0 0 X + 1 0 Z + Y → ( 2 ) Y Z X = 1 0 0 Y + 1 0 Z + X → ( 3 ) X Y Z + X Z Y = Y Z X → ( 4 )
Substituting equations ( 1 ) , ( 2 ) and ( 3 ) into equation ( 4 ) ,
1 0 0 X + 1 0 Y + Z + 1 0 0 X + 1 0 Z + Y = 1 0 0 Y + 1 0 Z + X → 1 9 9 X − 8 9 Y + Z = 0 → 1 9 9 X = 8 9 Y − Z → ( 5 )
X , Y and Z must be single digit integers.
As they are all distinct positive single digit integers, 8 9 Y − Z would be slightly bigger than 1 9 9 X .
By logic and a bit of arithmetic, the value of Y would be more than 8 9 1 9 9 + 0 = 8 9 2 0 0 ≈ 2 . 2 3 times but less than 8 9 1 9 9 + 1 0 = 8 9 2 0 9 ≈ 2 . 3 5 times the value of X .
In other words, 8 9 1 9 9 ≤ X Y < 8 9 2 0 9 .
The only pair of single digit integers where 8 9 1 9 9 ≤ X Y < 8 9 2 0 9 is when ( X , Y ) is equivalent to 4 , 9 . Thus we can conclude X = 4 and Y = 9 .
Substituting X = 4 and Y = 9 into equation ( 5 ) ,
1 9 9 X = 8 9 Y − Z → 1 9 9 ( 4 ) = 8 9 ( 9 ) − Z → Z = 5 0 1 − 4 9 6 = 5
Hence,
X Y Z = 4 9 5
Consider that X not equal to Z Z+Y = X+10 --------------------- (1) Z+Y+1 = Z+10 --------------------- (2) X+X+1 = Y
2X+1 = Y --------------------- (3) Z+2X+1 = X+10
X+Z = 9 ---------------------- (4)
Substituting (1)-(2), X-Z = -1 ---------------------- (5) 2X = 8 X = 4 Substituting X=4 in (3) Y = 9 Substituing X=4 in (4) Z = 9-4 = 5
495+459=954
I like this solution and can understand easily
From the (1) column we know that Z+Y = X, from the (2) column we know that Z+Y = Z. This is not possibile for hypothesis, unless we admit that Z+Y>10 so we have carry-over and X={Z-1, Y-1} o X=min{Z,Y}-1. Since the same sum appears in the (2) column, we have the carry-over also for this column, and, because the result under column (3) have one digit, it means that X≤4. So we have that 10<Z+Y≤14. We have some two possible set {Z, Y, X} = {5, 9, 4}, {9, 5, 4}. All the other set must be excluded because don't respect the rules. In particular we must remove also the second set, because if we have two number, x and y, the sum x+y≤17, so we can't have 9. This means that the correct choice is {Z, Y, X} = {5, 9, 4}
Well, we know that X must be < 5, since the answer is a 3-digit number.
We also know that Y has to equal either 0 or 9, since Y + Z = Z.
However, since X + X = Y, and X =/= 0, Y cannot be 0 (and therefore must be 9).
Now that we know Y is 9, X + X must equal 9. This is only possible with a carry from the tens place (4 + 4 (+1) = 9). Therefore X must equal 4.
For Z, we know that Z + 9 = 4. Z cannot be -5, and therefore must be 5 (5 + 9 = 4 with a carry of 1). This also works with the tens place.
Therefore XYZ = 495.
X must be smaller than 5. At each step assume x=i with i=1,..,4. For each x fixed, y could be 2x or 2x+1. For each value of y fixed, z is obtained looking at the units' column. Iterating this procedure at the step i=4 we have that y could be 8 or 9. For y=9 results z=5, finally 495
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In the ten's place, we have Y + Z = Z , this means that Y = 0 or Y = 9 . (9 being the case of having a carry forward from the unit's place).
However, because the result is three digit number, Y = 9 .
From this, we can say that X = Z − 1 (seeing the units place)
and also X = 4 (observing the hundred's place) and finally Z = 5 .
Which gives X Y Z = 4 9 5 .