# Electronics - Arithmetic Operations and Circuits - Discussion

Discussion Forum : Arithmetic Operations and Circuits - General Questions (Q.No. 11)
11.
Binary subtraction of a decimal 15 from 43 will utilize which two's complement?
101011
110000
011100
110001
Explanation:
No answer description is available. Let's discuss.
Discussion:
11 comments Page 1 of 2.

Brajendra Kumar Mishra said:   1 decade ago
I think answer will be (C).

43 = 1 0 1 0 1 1.
15 = 0 0 1 1 1 1.

Take the 2's complement of 15 =1 1 0 0 0 1.

Then add this value with binary equivalent of 43.

Will get,

1 0 1 0 1 1
+1 1 0 0 0 1
=1 0 1 1 1 0 0.

Then discard the carry output you will get 011100 so option will be (C).
We can verify it by taking simply 43 - 15 = 28.

When you will convert option C in decimal number that will give the correct answer that is '28'.

So option C is the correct answer.

@Brajendra.

Your way of subtraction is correct. But in the Question "will utilize which two's complement".

I think they ask value of the 2's complement which is used in that subtraction. So 2's complement of 15 = 1 1 0 0 0 1.

I don't agree with your answer @Nikhil, 2's comp can be made up after 1's compliment but you did it in a wrong way to make the answer correct.

Nisha said:   7 years ago
The question is that which 2's complement utilize.

And it is 15. It is subtracted and we make two's complement of it which is 110001.

43's two's complement is 010001.

15's two's complement is 0001.

Binary subtraction is 010000 may I know what is wrong in my answer.

Divij Mohan said:   10 months ago
Complement is only for negative numbers
43-15 = +28

Binary equivalent of +28 = 011100.

Option C should be the right answer
(1)

43 is 101011 --- (1).
15 is 1111 ----- (2).

Subtract (1)-(2)=110000.
And 2's comp of 110000 is 110001.

SPS said:   7 years ago