Numbers behind sound, pictures and video
Answers are for parents and teachers.
1
Add 0011 0101 and 0001 1010 (53 + 26) and check with decimal.
0100 1111 = 64 + 8 + 4 + 2 + 1 = 79, and 53 + 26 = 79.
2
Write −6 in 8-bit two’s complement (6 = 0000 0110) and check that 6 + (−6) gives 0000 0000.
Flip: 1111 1001; add 1: 1111 1010. Check: 0000 0110 + 1111 1010 = 1 0000 0000, the ninth bit is dropped, so 0000 0000.
3
A sound is recorded with 8,000 samples per second, 16 bits per sample, 2 channels, for 2 seconds. How many bytes (and KB with 1 KB = 1,000 bytes)?
8,000 × 16 × 2 × 2 = 512,000 bits = 64,000 bytes = 64 KB.
4
A 200 × 100 picture has 8 bits per pixel. How many KB (1 KB = 1,000 bytes)?
200 × 100 = 20,000 pixels × 8 bits = 160,000 bits = 20,000 bytes = 20 KB.
5
A clip of 60 KB is compressed to 12 KB. What is the compression ratio?
60 ÷ 12 = 5, so 5 to 1.