IndiaBIX

Aptitude - Problems on Numbers - Discussion

Discussion Forum : Problems on Numbers - General Questions (Q.No. 9)
Problems on Numbers
9.
In a two-digit, if it is known that its unit's digit exceeds its ten's digit by 2 and that the product of the given number and the sum of its digits is equal to 144, then the number is:
24
26
42
46
Answer: Option
Explanation:

Let the ten's digit be x.

Then, unit's digit = x + 2.

Number = 10x + (x + 2) = 11x + 2.

Sum of digits = x + (x + 2) = 2x + 2.

(11x + 2)(2x + 2) = 144

22x2 + 26x - 140 = 0

11x2 + 13x - 70 = 0

(x - 2)(11x + 35) = 0

x = 2.

Hence, required number = 11x + 2 = 24.

Discussion:
42 comments Page 2 of 5.
Sabu said:   7 years ago
11x2 + 13x - 70 = 0.
(x - 2)(11x + 35) = 0.
x = 2.

How does this do?
(3)
Moti Chavan said:   8 years ago
Yes, right @Pratyasha.

The 2 digit number is represented as 10x+y. But by taking like this I'm not getting answer.
Pratyasha said:   8 years ago
Because a 2-digit number is represented as 10x+y.
Naina said:   9 years ago
Hi,

Can anyone tell me, Why we can't take 10x at ten's place and Y at an unit place?
Nisha said:   9 years ago
How did you factorise the equation?

Please help me to solve it.
Shiwani said:   9 years ago
Why we added x instead of 10x to (x+2)?
(1)
Akash said:   9 years ago
The simple method is to check the option.

Options B and C are wrong because of their option B] difference is not 2 and option C] unit digit is greater than 2. So this is neglected.

Now remaining option is 24 checks it 24 * (2 + 4) = 144 is true then it's a right answer.
(2)
Anjali said:   9 years ago
Correct answer @Naresh.
BASAVRAJ said:   9 years ago
Well said. Your explanation is good @Naresh.
Anjali said:   9 years ago
Kindly explain it in any another method, I could not understand it.
Post your comments here:

Your comments will be displayed after verification.

Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers