Aptitude - Problems on Numbers - Discussion
Discussion Forum : Problems on Numbers - General Questions (Q.No. 5)
5.
A two-digit number is such that the product of the digits is 8. When 18 is added to the number, then the digits are reversed. The number is:
Answer: Option
Explanation:
| Let the ten's and unit digit be x and | 8 | respectively. |
| x |
| Then, |  |
10x + | 8 |  |
+ 18 = 10 x | 8 | + x |
| x | x |
10x2 + 8 + 18x = 80 + x2
9x2 + 18x - 72 = 0
x2 + 2x - 8 = 0
(x + 4)(x - 2) = 0
x = 2.
Discussion:
42 comments Page 5 of 5.
Vinod said:
10 years ago
Two digit number 10x+y.
xy = 8.
10x+y+18 = 10y+x.
x-y = -2.
(x+y)^2 = (x-y)^2+4xy.
= (-2)^2+4*8 = 36.
x+y = 6.
x-y = (-2).
x = 2.
y = 4.
Answer 24.
xy = 8.
10x+y+18 = 10y+x.
x-y = -2.
(x+y)^2 = (x-y)^2+4xy.
= (-2)^2+4*8 = 36.
x+y = 6.
x-y = (-2).
x = 2.
y = 4.
Answer 24.
Saradhapriyanka.s said:
2 decades ago
I could not understood your answer, please explain in some other way.
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