Answers to Writing Assignment 5

1. 1011 = 11 (8 + 2 + 1)
101010 = 42 (32 + 8 + 2)
11111 = 31 (16 + 8 + 4 + 2 + 1)
10010 = 18 (16 + 2)

2. 31 = 16 + 8 + 4 + 2 + 1 = 11111
51 = 32 + 16 + 2 + 1 = 110011
7 = 4 + 2 + 1 = 111
103 = 64 + 32 + 4 + 2 + 1 = 1100111

3. Suppose that we want to download a 100 MB file. How long will it
take on each of the following connections?

1. A modem that can download at 56 kilobits/second
56 kilobits/sec * 1byte/8bits = 7 kilobytes/sec
100 Megabytes * 1024 kilobytes/megabyte = 102400 kilobytes
102400 kilobytes / 7 kilobytes/sec = 14,628 sec = 243 minutes =
4.05 hours.

(with 1000 KB = 1 MB)

56 kilobits/sec * 1byte/8bits = 7 kilobytes/sec
100 Megabytes * 1000 kilobytes/megabyte = 100000 kilobytes
100000 kilobytes / 7 kilobytes/sec = 14,285 sec = 238 minutes =
3.97 hours.

2. A DSL connection that can download at 5 Megabits/second

5 megabits/second * 1 byte/8 bits = 0.625 megabytes/sec
100 megabytes / 0.625 megabytes/sec = 160 seconds = 2.66 minutes

3. A high-speed connection that can download 10 Megabits/second
10 megabits/sec * 1 byte/8 bits = 1.25 megabytes/sec
100 megabytes / 1.25 megabytes/sec = 80 seconds = 1.33 minutes

4. If we have an Internet connection that can upload 3
Megabits/second, and an MP3 is 60 Megabytes, how many MP3s can we
upload in an hour?
3 megabits/sec * 1 byte/8 bits = 0.375 megabytes/sec
60 megabytes / 0.375 megabytes /sec = 160 seconds to upload one
MP3.

Since there are 3600 seconds in a hour, we can upload 3600 / 160 =
22.5 MP3s.

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