Convert decimal 99 to binary.
A. 1100101
B. 1101001
C. 11100011
D. 1100011

Hint: Binary numbers are constructed from right to left. If the decimal number is even put zero, if odd put 1. Divide 99 by 2 and check if the number is odd or even. Then divide the number again by 2 and check until we get 1.

Complete step-by-step answer:
The binary number is constructed from right to left. If the decimal number is even, we write a 0. If it’s odd we write 1. Then divide the number into two and round down. Again repeat the process until you get to 1.
We have been decimal number 99 to convert it to binary.
99 is an odd number, so start with 1.
Divide 99 into two, we get 49.5, and let us round it to 49.
49 is an odd number so add 1 on the left = 11.
Let us divide 49 again into two, we get 24.5, and let’s round it to 24.
24 is an even number so add a zero so add a 0 to the left = 011.
Now divide 24 into two, we get 12. 12 is an even number so add another 0 to the left = 0011.
Now divide 12 into two, we get 6, which is an even number. So add 0 to the left = 00011.
Now let us divide 6 into two. We get 3 which is odd. So add 1 to the left = 100011.
Now let us divide 3 into two. We get 1.5, let us round it to 1, so 1 is an odd number. Add it on the left = 1100011.
Hence, 99 is 1100011 in binary.
Option D is the correct answer.

Note: You can memorize the ones and zeroes by keeping track of positions with fingers. Keep fingers by side or on the table in front of you. Since it’s calculated from right to left, the 1^st binary digit would be represented by you right and each additional digit would move to the left.