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:
43 comments Page 3 of 5.
Mahesh said:
9 years ago
Could anyone please provide the shortcut method?
Dipak said:
9 years ago
xy = 8
10x + y + 18 = 10y = x
9x - 9y + 18 = 0
x-y = -2
8/y - y = -2
So by solving above equation we get y = 4,
by putting y=4 in xy=8 so we get x = 2.
So the original no. is 10x+y = 24.
10x + y + 18 = 10y = x
9x - 9y + 18 = 0
x-y = -2
8/y - y = -2
So by solving above equation we get y = 4,
by putting y=4 in xy=8 so we get x = 2.
So the original no. is 10x+y = 24.
Sunil said:
9 years ago
The sum of five numbers is 18, their average is 3. 6 and their difference is 1. What are the numbers?
Can anyone tell me the answer?
Can anyone tell me the answer?
Naina said:
9 years ago
Hi @Gopinath.
How 8+18 = 24?
I think its 26.
How 8+18 = 24?
I think its 26.
Dinesh said:
1 decade ago
@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.
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.
Chandra said:
2 decades ago
There are only four two digit numbers whose product of the digits is 8. They are 18, 81, 24 and 42.
We can get easily 24 is the answer.
We can get easily 24 is the answer.
Sun said:
2 decades ago
We can directly check out the answer through options.
24 + 18 = 42 which gives product 8.
24 + 18 = 42 which gives product 8.
Shanthi said:
2 decades ago
It is very simple. You can get answer from the options itself. 18+18=36 no. Not reversed. Tak 24+18=42 no. Reversed. 24 is reversed as 42.
Sudheer said:
1 decade ago
Products of 8 is 2*4, 4*2, 8*1, 1*8.
But he is telling by adding 18 to it the digits are reversed means 24+18=42.
24 is changed to 42. So, the answer is 24.
But he is telling by adding 18 to it the digits are reversed means 24+18=42.
24 is changed to 42. So, the answer is 24.
May said:
1 decade ago
Oh. You great and feeling in so easy. Thanks you.
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