Aptitude - Problems on Numbers - Discussion

Can anyone explain what happens after 12k = 48 and 21k = 84?

After we do this how do we get the final answer?

Consider no is 10x + y.
Then according to first condition (10x + y) - (10y + x) = 36.
On solving this we get, (x - y) = 4.
In, the last condition they give, y/x = 1/2.
By solving both above equations we get y = 4.

They ask the value for,(10x + y) - (10x - y).
Which is equal to 2y.
Put the value of y.

We get final value = 8.

Hi can anyone explain when to take 2x and x and when 10x+y-10y-x?

The Problem should be re-stated specially on the aspect of the ratio.

It should "NOT JUST BE" 'if the ratio between the digits of the number is 1:2. But it should be restated as 'if the ratio between the unit's and ten's digits of the number is 1:2.

Then if that's ok, I think reliably be solvable!

Thanks for the explanation.

Let digit at 10th place X and unit place Y.

From the question:

10X+Y-(10Y+X) = 36.

So, 10X-X+Y-10Y = 36.

= 9X-9Y = 36.

= X-Y = 4.

From question Ratio is 1x:2x.

Difference between the ratio 1x.

So 1x = 4 and 2x = 8. Sum and difference of these two 12, 4 respectively. Then difference between these two 8. Got answer.

Assume the 2 digit number be 84 and by interchanging the digits we get 48.

Difference 84-48 = 36.
Sum = 4+8= 12.
Difference = 8-4 = 4.

Difference between sum & diff = 12-4 = 8.

Why are you taking (10*2x+x) - (10+2x) = 36? Please explain it.

Hello Friends,

Suppose x & y two digits and the ratio b/w the digits of the number is 1:2

Therefor, x:y = 1:2
So, y = 2x ..........equation 1.

Hence, y is in ten's position and x is in unit place.

According to the question,
(10y + x) - (10x + y) = 36

From equation 1, we get y = 2x
(10*2x + x ) - (10x + 2x) = 36
(20x + x) - (12x) = 36
21x - 12x = 36
9x = 36
x = 4 ........... equation 2.

Now putting the value of x in equation 1.
y = 2*4
y = 8

Sum and the difference of the digits of the number (x + y) & (x - y) respectively.

According to question,
Difference between (x + y) & (x - y).
= (y+ x) - (y - x) ............. equation 3.

Putting the value of x = 4 & y = 8 in the above equation.
We get,
= (8 + 4) - (8 - 4).
= 12 - 4.
= 8.

Can anyone explain why do we take (y+x)-(y-x) in the last step rather than 10x+y-(10y-x) ?