| Title: | Mathematics at DEC |
| Moderator: | RUSURE::EDP |
| Created: | Mon Feb 03 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2083 |
| Total number of notes: | 14613 |
Hi there,
My step daughter recently sat for a US "PSAT" test here in Australia (she
is a US citizen). On seeing the results, I am convinced that one of the
official answers is incorrect. Before sending any overseas letters, I'd like
to get an opinion from the MATH readership. I won't say what the correct
answer is supposed to be to avoid prejudgement. Here is the question:
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PSAT October 20th 1990
Question 34 in Maths section
If x�+x-12 < 0 what is the greatest integer value that x can have?
a) -4
b) -1
c) 0
d) 2
e) 3
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So what would your answer be?
John Gillings, Sydney CSC
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1358.1 | (d) | CHOVAX::YOUNG | Give peace a chance. | Thu Dec 20 1990 23:02 | 1 |
| 1358.2 | JARETH::EDP | Always mount a scratch monkey. | Fri Dec 21 1990 08:10 | 4 | |
Yes, it's d. What answer did the test have?
-- edp
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| 1358.3 | GUESS::DERAMO | Dan D'Eramo | Fri Dec 21 1990 12:15 | 1 | |
(d) 2 | |||||
| 1358.4 | moderators, am I allowed to repost these here? | GUESS::DERAMO | Dan D'Eramo | Fri Dec 21 1990 12:17 | 39 |
I wonder if these are relevant here:
<<< 2B::NOTES1:[NOTES$LIBRARY]MATH.NOTE;7 >>>
-< Mathematics at DEC >-
================================================================================
Note 1357.3 Representation of cones in R^2 3 of 4
SHIRE::ALAIND "Alain Debecker @GEO DTN 821-4912" 19 lines 21-DEC-1990 06:15
--------------------------------------------------------------------------------
> re .-2
>
> You twice use "positive" where I think you mean
> "nonnegative"
A matter of culture. In many countries, zero is taken as a
number both positive and negative, and the sentence "x is
smaller than y" means x <= y. In US and UK, zero is neither
positive nor negative, and "x is smaller than y" doesn't
allow for equality.
Nevertheless, you are right. I was lousy on the edges:
Note that the condition (4) is equivalent to the fact that
the cone is closed. An *open* set verifying condition (1)
to (3) is of the form K = { su + tv | s,t > 0 }. The same
demonstration holds: this time, the intersection of K and
the cone is open, thus of the form ]u,v[ instead of [u,v].
================================================================================
Note 1357.4 Representation of cones in R^2 4 of 4
CHOVAX::YOUNG "Give peace a chance." 7 lines 21-DEC-1990 11:38
-< But this is English, right? >-
--------------------------------------------------------------------------------
Re .4:
But these are fairly precise terms in English. For instance,
"Positive" in English has a precise meaning, ie. "Greater than
zero."
-- Barry
| |||||
| 1358.5 | re .0 | EAGLE1::BEST | R D Best, sys arch, I/O | Fri Dec 21 1990 17:40 | 15 |
The equation factors into (x-3)(x+4) < 0. This requires either x-3 > 0 AND x+4 < 0 OR x-3 < 0 AND x+4 > 0 No value of x can satisfy the first conjunction. The second conjunction can be rewritten as -4 < x < 3. The greatest integer x meeting this (assuming greatest means most positive and not largest absolute value) is 2. You take the PSAT in Australia ? My but ETS has a long reach. | |||||
| 1358.6 | math good, reading bad :*( | GIDDAY::GILLINGS | a crucible of informative mistakes | Sat Dec 22 1990 04:00 | 15 |
Thanks for the replies.
d (2) was indeed the answer I was looking for. On triple checking I
found that both myself and my wife misread the answer sheet. We thought
the official answer was E (3) but it was D :*( (is that a red face?)
>You take the PSAT in Australia ? My but ETS has a long reach.
US citizens (like my step daughter) may take PSAT and SAT exams if
they wish. Heidi was just practicing as she is only 15 (year 10). She will
do a "real" one next year. Despite getting this question wrong, she
still managed a 96th percentile result :-).
John Gillings, Sydney CSC
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| 1358.7 | GUESS::DERAMO | Dan D'Eramo | Sat Dec 22 1990 21:09 | 3 | |
Tell her, "Congratulations!"
Dan
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