NIELIT 2021 Dec Scientist B - Section B: 81

Question

The two numbers represented in Signed $2’s$ complement form are

$\text{A} = 11101101$ and $\text{B} = 11100110.$ If $\text{B}$ is subtracted from $\text{A},$ the value obtained in signed $2’s$ complement is $:$

• A. $111000101$
• B. $00000111$
• C. $11111000$
• D. $10000011$

Comments

-19-(-26) = 7

2’s complement representation of +7=00000111

So,Answer is B.

Answer 1

A=11101101= -19  ---> 00010011(in 2's)= 19(decimal)

B= 11100110= -26  --> 00011010 (in 2's) = 26(decimal)

When we do 2's complement of +ve binary number we get -ve binary number and vice versa.

Now B is subtracted from A (in decimal form):       A-B= -19 -(-26)= -19+26= 7.

(in binary form): A-B = A+(- B)= A + (2's of B) 

11101101(-19)  + 00011010(+26) = 100000111  (1 is doesn't considered, it is carry out), hence answer is only 00000111 which is 7 in decimal.