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SAT prep
- Thread starter NRS
- Start date
NRS said:I'm not quite sure where to post this, but here it is:
Let # be defined by z # w = zw. if x=5 # a, y= 5 # b, and a+ b= 3, what is the value of xy?
My comment removed....since I obviously was incorrect.
D
Deleted member 4993
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NRS said:I'm not quite sure where to post this, but here it is:
Let # be defined by z # w = zw. if x=5 # a, y= 5 # b, and a+ b= 3, what is the value of xy?
Are you sure it is (zw) and NOT z[sup:n9wr950h]w[/sup:n9wr950h]
If z#w = z[sup:n9wr950h]w[/sup:n9wr950h] - then the answer would make sense.
Assuming all that verbiosity means:NRS said:I'm not quite sure where to post this, but here it is:
Let # be defined by z # w = zw. if x=5 # a, y= 5 # b, and a+ b= 3, what is the value of xy?
x = 5a
y = 5b
a + b = 3
Then:
x + y = 5(a + b) = 5(3) = 15
and:
xy = (5a)(5b) = 25ab
IF xy = 125 as you stated, then 25ab = 125 ; ab = 5
Evident that ab = 5 and a+b = 3 is impossible:
with b = 3 - a, then:
a(3 - a) = 5
a^2 - 3a + 5 = 0
a = [3 +- sqrt(-11)] / 2
Soooo: there is a typo in your question; agree?
Btw, if a + b = 6, then all's swell !
First of all, thankyou very much for the effort, but... I quoted that exactly from the SAT prep book (a practice test to be exact) and rechecked my typing. Second, the fact that the answer is 125 wasn't defined in the question, I found it in the answer key when I checked my answers. Also, I brought the book to the college I take classes at, and stumped 2 tutors and a math professor!
I thought about solving it as a system of equations or plugging it into a matrix, but the variable to equation ratio isn't right. Is it unsolvable? and if so, WHY is it in a highschool SAT prep practice test!!?? :?
I thought about solving it as a system of equations or plugging it into a matrix, but the variable to equation ratio isn't right. Is it unsolvable? and if so, WHY is it in a highschool SAT prep practice test!!?? :?
I told you it was unsolvable; why are you asking?NRS said:Is it unsolvable? and if so, WHY is it in a highschool SAT prep practice test!!?? :?
"THEY" probably made the typo; I told you that using a+b=6 (instead of a+b=3) WORKS FINE.
D
Deleted member 4993
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NRS said:I'm not quite sure where to post this, but here it is:
Let # be defined by z # w = zw. if x=5 # a, y= 5 # b, and a+ b= 3, what is the value of xy?
This is very "ill-worded" question - very unlike SAT problems (which are very "well-worded).
For example:
does it mean:
3#7 = 37 or (3*7=) 21
You forgot a quotation symbol at end of well-worded;Subhotosh Khan said:This is very "ill-worded" question - very unlike SAT problems (which are very "well-worded).
this will be duly noted on your file flap, and will be taken in consideration at your annual performance review.