- Numerical Mathematics - Reported problems
- Week 1
- Week 2
- Video: 1.401 Octal and hexadecimal (integer)
- Practice quiz: 1.404 Translate between decimal and hexadecimal or octal (fractional)
- FIXED - Video: 1.405 Special relationship between binary and hexadecimal, and binary and octal
- Practice quiz: 1.406 Translate between binary and hexadecimal/octal
- Practice quiz: 1.602 Arithmetic in hexadecimal/octal
- Week 3
- Week 4
- Week 5
- Week 6
- Week 7
- Week 8
- Week 10
- Week 12
- Week 13
- Week 14
- Week 15
- Week 17
- Additional resources
This page is about the numerical mathematics module.
- At 11:16,
(255, 255, 255)is white, not blue.
- At 11:34: Wrong. Each column is a power of 60, so it should be times
1, times60and times3600.
- At 0:37: The "fractional point" is called "radix point".
-
Answers should be given without spaces.
-
When a repeating fractional part is present, the answer should be written as
i.rr..., whereistands for integer part,ris the repeating fraction and one must include three dots at the end. Example:
is written as
- In the quiz at 3:41, the place values are supposed to be entered as "1, 16, 256". The answer isn't accepted.
- In the quiz at 4:24, 65536 should be written as
, but the "6" isn't part of the exponent part. - At 5:07, second letter in hexadecimal should be "B", not "D".
- At 6:01, the hexadecimal number
11Fshould have an expansion starting with
, not 
as displayed. - In the quiz at 6:29, the third answer is 256, not 64. The last part is asking in the quiz for multiples in binary while the answer is given for hexadecimal.
3.44in octal is
, not 
.- Options may present groupings of numbers. If a grouping is supposed to be of 3 digits for instance and you're presented with 4 digits, assume that the last digit should be in subscript (representing the number base, such as 2 for binary or 8 for octal) so that it makes sense when reading. In a grouping of 3 digits,
0002should be interpreted as000, base2.
- At 7:38, this is wrong.
C(base 16) = 12 (base 10) = 1100 (base 2), not 1101. - At 11:24, The grouping of digits is wrong.
in binary should read 
, having only one radix point. - At 11:37, it is said the answer is
11.71(base 8). Wrong: It's11.74(base 8).
- Question 6:
73.06(base 8) is111011.00011in binary.
6D × 60in hexadecimal is28E0.6C × 3Bin hexadecimal is18E4.
- At 27:20, 83 is not 255 but 512.
- At 1:49, the expression isn't rendered properly (the congruence symbol doesn't appear). Subsequent expressions also present this issue.
-
The video contains many display errors that are fixed in a previously uploaded version. While not being flawless, it's much better. For now, the video can be downloaded from this link. If you want to add subtitles, you can download them here.
- If you don't know how to add the subtitles to the video, try with VLC media player (free): open the video (
1_1101_Encryption_using_modular_arithmetic.mp4) and from VLC, click at the top onSubtitle, then onAdd Subtitle File...and open the subtitles file (1_1101_subtitles-en.vtt). They will automatically be added and synced to the video.
- If you don't know how to add the subtitles to the video, try with VLC media player (free): open the video (
-
At 3:43, a banner appears in the background and has nothing to do with was it being taught.
-
At 4:40 and 4:52, the congruence symbol is not rendered properly:
. -
At 6:04, it should be
, not 
. -
At 8:43, the equation appears in the background and can't be read. The equation is:
. -
At 11:28, again the expression can't be read. The expression is:
.
- Audio is out of sync from 15:19 onward: please refer to the transcript to better follow along.
Partially fixed. The transcript and subtitles do not appear at this moment.
- At 20:38, the number
32was skipped when calculating the sum of the series.
- At 10:11, the summation for the term
is omitted.
- Question 1: There is no clear way to indicate that there is no limit or what the considered interval really is.
- The result for the last example is
, not 
.
- Question 1: The answer is
divergent. - Question 2: The answer is
convergent,3/4.
- Question 2: The quiz does not accept the valid answer and tells the user that the wrong answer is correct instead.
- There is no sound. For now, you can download the video from this link. You can get the subtitles from this link.
- If you don't know how to add the subtitles to the video, try with VLC media player (free): open the video (
3_101_cartesian_coordinates.mp4) and from VLC, click at the top onSubtitle, then onAdd Subtitle File...and open the subtitles file (3_101_subtitles-en.vtt). They will automatically be added and synced to the video.
- If you don't know how to add the subtitles to the video, try with VLC media player (free): open the video (
- At 10:44,
, not 
.
- At 4:17, the result of
is 
, not 
.
- There is no sound nor visual guidance from 8:16 till 8:35.
- At 8:00, the last formula presented at the bottom of the slide should not have
but 
instead, as follow: 
- No formatting seems appropriate to answer question 2. None of the following is accepted:
inf,infinity,infty.
- At 17:09,
, not 
.
- Questions 6 and 7 present different errors:
- The information in the question doesn't necessarily match the data in the picture.
- The grader expects impossible answers for the missing side and/or angle. Verify your answer with Pythagoras's theorem and the sine rule instead of relying on the grader.
- At 14:03,
, not 
.
- Question 1: The given angles in the selection are computed correctly, but they do not correspond to the correct letter: the value of angle C should be the value of angle A and vice versa.
- Question 4: The grader appears to consistently invert the solution when converting from radians to degrees. For example, 40 radians is ~131.83° but the expected answer is 0.698°, which is the result in radians of 40°.
- [fixed] The quiz doesn't let the student see what the mistakes are once the quiz has been submitted.
- Question 3: The answer should be None of the other options is correct when asked for a value of
where 
.
- Question 2: The option
is valid and should be selected, but is currently marked as wrong. - Question 3: Some translations that should occur in the negative x-direction, such as
, are mistakenly graded as being in the positive x-direction.
- At 14:40, a negative sign is added to
. The equation should instead be: 
- Question 1: The selection is invalid.
should not be selected as it is not equivalent to the right answer, which is also another available option to select: 
- At around 3:45, the final expression for the derivative of
is missing a negative sign in front of it. The correct expression should be as follow:
- Questions 5 and 6 assume
, which is indispensable to know to calculate the limit.
- At 4:16, the notation for the vector is wrong. It should instead be:
- At 9:48, the resulting matrix contains an error at row 2, column 4. The correct value is 122 as shown in this matrix:
- The video blacks out from 2:53 onward.
- Page 423: Minor mistake in carrying calculations:
