Aptitude - Problems on Numbers - Discussion

@Vijay.

Its very simple.

See the no 9 is divisible by only 3 (other than 1 & itself not to be considered).

So to make 7*5462 divisible by 9, * must be 0 or 3.

Trying with 0 fails to give the ans so then try with 3 it gives u the correct answer.

Let me explain the simplest way.
The way is,

Let take two digit no as x and y.

x * y = 8.
xy + 18 = yx.

//xy = 8// .

8+18 = yx.
yx = 24.

Why 18 should be added in the option to get the answer?

Two digits=x & y so two digit no = 10x+y.
Product of digits is x*y = 8.

So (10x+y)+18 = 10y+x.
i.e x-y = -2......(1).
as x*y=8 so x = 8/y.

Hence equation (1) becomes 8/y-y = -2......(2).
Solving equation(2) we get y = 2.

Putting y=2 in equation (1) we get x = 4.
So the two digited number xy = 42.

So please tell me how answer comes to 24.
Please correct me if I am wrong?

Above you write 8+18 = 24 but 8+18 is 26 how it is to be 24?

First we have to check with the options then only we find answer easily.

Here the first condition is that the multiple of that two digit number is 8.
Then we check all the options. Given four options satisfying the 1st condition.

Now go to 2nd condition, i.e if 18 is added to that two digit number the answer will be reversed.
So we can check through all the options then we get 24 is the correct option.

i.e 2*4 = 8.
24 + 18 = 42.

Hence the 2 conditions are satisfied.

How can solve like this manner 8+18 = 24?

8+18 = 26. It's wrong. The product of the number is 8 not that number.

Only 24 is the product of 8 in this number. So answer is 24.

Can you said in another way?

9x2+18x-72.

How it is simplified further?