SOLUTION: Find a two digit number such that three times the tens digit is 2 less than twice the units digits and twice the number is 20 greater than the number obtained by reversing the di

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Question 1163926: Find a two digit number such that three times the tens digit is 2 less than
twice the units digits and twice the number is 20 greater than the number
obtained by reversing the digits

Found 5 solutions by Edwin McCravy, AnlytcPhil, greenestamps, MathTherapy, josgarithmetic:
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
I won't do yours for you but I'll do one exactly like it, step by step. You
can use it as a model to do yours by.

So instead of your problem, I'll do this one:

Find a two digit number such that six times the tens digit is 8 less than
four times the units digits, and three times the number is 23 greater than the
number obtained by reversing the digits.
The tens digit is t
The units digit is u
The number is 10t+u
The number obtained by reversing the digits is 10u+t

(1)   6t = 4u - 8
(2)   3(10t+u) = (10t+u) + 23

Simplify the equation (2)

      30t + 3u = 10u + t + 23
      
Subtract 10u from both sides

      30t - 7u = t + 23

Subtract t from both sides

(3)   29t - 7u = 23

Now solve equation (1) for t

(1)   6t = 4u - 8

Divide both sides by 6

(4)      t = (4u-8)/6

Substitute in equation (3)

(3)    29t - 7u = 23  
  
29(4u-8)/6 - 7u = 23

Multiply through by 6

 29(4u-8) - 42u = 138 

 116u-232 - 42u = 138

      74u - 232 = 138

Add 232 to both sides

            74u = 370

Divide both sides by 74

              u = 5 

Substitute in equation (4)

(4)      t = (4u-8)/6

         t = [4(5)-8]/6

         t = [20-8]/6

         t = 12/6

         t = 2

So t = tens digit = first digit = 2
and u = units digit = second digit = 5

So the two digit number is 25.

Now use this as a model to do yours by.

Edwin

Answer by AnlytcPhil(1806) About Me  (Show Source):
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Here is a very different method for solving the problem....

Let t and u be the tens and units digits, respectively. Then we are told

3t+=+2u-2

Solve that single equation for t and use logical reasoning to find possible values for t and u, knowing that they are both positive single-digit integers.

t+=+%282u-2%29%2F3
t+=+%282%28u-1%29%29%2F3

Since t has to be a positive integer, and since 2 is not divisible by 3, (u-1) must be positive and divisible by 3.

That means there are only two possible values for u: 4 and 7.

That in turn leads to only two possible values for the 2-digit number: 42 and 74.

Only one of those satisfies the other condition of the problem.


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
Find a two digit number such that three times the tens digit is 2 less than
twice the units digits and twice the number is 20 greater than the number
obtained by reversing the digits
Let tens and units digits, be T and U, respectively
Then we get:            
                                                            12T - 8U = - 8 ------- Multiplying eq (i) by 4 ------ eq (iii) 
                                                             7T = 28 ------ Subtracting eq (iii) from eq (ii)
                                                             Tens digit, or matrix%281%2C5%2C+T%2C+%22=%22%2C+28%2F7%2C+%22=%22%2C+4%29

3(4)  -  2U = - 2 ------- Substituting 4 for T in eq (i)
12  -  2U = - 2
-  2U = - 14
Units digit, or matrix%281%2C5%2C+U%2C+%22=%22%2C+%28-+14%29%2F%28-+2%29%2C+%22=%22%2C+7%29

highlight_green%28matrix%281%2C2%2C+%22Number%3A%22%2C+47%29%29

Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Using variables t for the tens digit ad u for the units digit, the description is written as system%283t=-2%2B2u%2Cand%2C2%2810t%2Bu%29=20%2B%28t%2B10u%29%29;
and you want to calculate what is 10t%2Bu.
.
.
system%28-3t%2B2u=2%2C19t-8u=20%29

system%28-12t%2B8u=8%2C19t-8u=20%29

ADD the equations,....
t=4


2u=3%2A4%2B2substitutionused:
2u=14
u=7


RESULT: 10t%2Bu=highlight%28highlight%2847%29%29