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Finance charge 2019-01-03
From Kenneth:

Hello Math Central:

The calculation for determining the finance charge per \$100.00 (FC/100) is determined by the following:

Finance Charge/Amount financed * \$100.00 = the finance charge per \$100.00

Since the denominator (amount financed) is not multiplied by \$100.00, how does the result equal the finance charge per \$100.00? The numerator (finance charge) is the only amount multiplied by \$100.00.

Example 1.  3/4 * 6 = 18/4 not 18/24 The 4 is not multiplied by the 6.

Example 2.  \$49.00/\$200.00 * \$100.00 If \$49.00 is divided by \$200.00 the result is \$0.245/\$1.00. If \$0.245/\$1.00 * \$100.00 = \$24.50/\$1.00. This answer is not \$24.50/\$100.00.
How does the above equal the finance charge per \$100.00 when the denominator is not multiplied by \$100.00?

If the division is not used to indicate the \$0.245 per \$1.00, the result becomes \$49.00/\$200.00 * \$100.00 = \$4,900.00/\$200.00.

..........

Kenneth

The intersection of a curve and a line 2018-03-08
From lola:
find the set of values of constant C for which the line y=x+c intersects the curve y=2 square root x at, at two distinct points
The evaluation of a 3 by 3 determinant 2016-02-19
From Kristen:
What is the step-by-step process on how to evaluate the determinant of a 3*3 matrix, using the expansion method (not the diagonal method)
Fractions of two quantities 2016-01-22
From Melody:
Kate ate 1/4 of her orange. Ben ate 2/4 of his banana. Did Kate and Ben eat 3/4 of theit fruit? Explain.
From itsel:
Find the discriminant ans use it to determine the use the quadratic formula to solve the equasion -2x^2+3x+2=0
The discriminant 2010-01-17
From Sonjonnia:
What is the value of the discriminant?
16x^=16x-4

The adjacency matrix of an undirected graph 2010-01-15
From Bhavya:
Let Cn be the undirected graph with vertex set V = {1,2,3,...,n} and edge set E = {(1,2), (2,3), (3,4),.... , (n-1,n), (n,1)}. Let An be the adjacency matrix of Cn.
a. Find the determinant of An.
b. Find (An)^2

An annuity 2009-02-27
From Jules:
R 20 000 is deposited in the bank,at the end of each year R 5 000 is withdrawn from it, the interest is 13 percent compounded monthly. Calculate how many years that person will be able to use his/her money ?
Nullity 2009-02-16
From Justin:
What exactly does the term nullity mean in the context of transreal numbers invented by Dr. James Anderson?

All the Best,

Justin

4 by 4 determinants 2008-06-27
From rav:
How to solve problems of determinants which has four rows and four columns& please give me easy tips to solve permutations and combinations problems.
Determinants 2008-05-02
From Henry:
I have a question about solving 3x3 matrices.

The traditional way, or at least the way I've been taught, is that if one has a 3x3 matrix such as:

[ a b c ]
[ d e f ]
[ g h i ]

one solves it according to this formula:

[ei - hf) - (bi - hc) + (bf - ec) = determinant.

According to a book I'm now studying to prepare for the California CSET exam, there is another, easier, way to solve it:

[ a b c ] [ a b ]
[ d e f ] [ d e ]
[ g h i ] [ g h ]

In other words, one repeats the first two rows of the matrix and adds them to the right.

At this point, the determinant is calculated thus:

(aei) +(bfg) + (cdh) - (gec) - (hfa) - (idb).

Is this, in fact, correct?

Area of a 17-sided lot 2007-11-21
From Lynda:
My uncle is wanting to buy this piece of land [a 17-sided polygon] but we are questioning the acerage total. the measurements are [on the attached diagram].
A matrix of polynomials 2007-07-18
From Mac:

Let A be a n*n matrix, the elements of which are real (or complex) polynomial in x. If r rows of the determinant becomes identical when x=a, then the determinant
A) has a factor of order r
B) has a factor or order > r
C) has no factor
D) has a factor of order < r

Values of k for which k(x^2+2x+3) - 4x - 2 is never negative 2007-06-29
From claire:
Find the range of values of k for which k(x^2+2x+3) - 4x - 2 is never negative.
The roots of (x - k)(1-3x) + 1 = 0 2007-06-28
From Claire:
Show that the roots of (x - k)(1-3x) + 1=0 are real and distinct for all real values of k. Hence, or otherwise, find the range of 9sin^2 r - 6sin r + 13
Evaluating a determinant 2007-02-25
From Suud:
Please send me the detailed steps of calculating the determinant of the following 4by4 matrix -1 -3 1 2 -2 0 -1 1 3 2 0 4 0 -3 1 -2
My wife's recent pregnancy, 2006-07-24
From Tom:
During my wife's recent pregnancy, it so happened that my wife's 29th birthday fell on the exact same day that her unborn child was 29 weeks old (i.e. it was 29 x 7 days from the date of conception as advised by the doctor) I would like to know what the probability is of the above event occurring for a randomly chosen pregnant woman i.e. that the pregnant mum's x'th birthday falls on the same day that the unborn child is x weeks old EXACTLY.
Discriminant 2005-06-20
From A student:
If a quadratic has real root, its discriminant b2-4ac>=0 Is there any similar condition or method by which you can find whether roots of a cubic equation are real or not?
A matrix problem 2005-04-04
From Alan:
 Let A = 1 -1 0 2 -1 2 a b c

where a, b, c are constant real numbers. For what values of a, b, c is A invertible? [Hint: Your answer should be an equation in a, b, c which satisfied if and only if A is invertible.]

From Mike:
Byron lives where people trade goods they produce for other things they need. He has some fish and wants to trade them for bananas. He finds the following:
5 fish = 2 loaves of bread
6 oranges = 2 melons
1 loaf of bread = 1 banana and 3 oranges
4 loaves of bread = 14 oranges
How many bananas can Byron get with 5 fish?

A metric prefix table 2004-03-07
From April:
Can you tell me what the scale is for nano, micro, mega, kilo, etc.... I know that mega is 10 to the sixth power but I can't remember the other ones.
A determinant 2003-02-13
From A student:

I have to find the determinant of the following matrix

 -2 3 1 2 4 -3 0 -2 5 1 4 2 1 -3 5 2 3 4 -1 2 6 0 3 2 -4

Expanding determinants using minors 2001-02-20
From A student:
Question:
1) Determinants by expansion by minors.

i)
| 1 2 1 2 1 |
| 1 0 0 1 0 |
| 0 1 1 0 1 |
| 1 1 2 2 1 |
| 0 1 1 0 2 |

Banana yogurt 2000-11-03
From James:
A grocery store has 100 cartons of banana yogurt in stock.Each carton contains 12 cup of banana yogurts.The probability that a cup has fewer than 20 banana chunks in it is 10 %. So,What is the probability that between 15 and 25 (inclusive) cartons out of the 100 cartons have exactly 3 cups with fewer than 20 banana chunks?
Transporting bananas 2000-10-18
From Krystie:
A farm has 45 bananas, a man has to take a truck and transport 15 bananas to a market that is 15 miles away. Every mile he travels, he must eat a banana. I have to get at least one banana to the market
Rule of 78 2000-03-22
From Dan Baumgarten:
Can you explain the rule of 78 and the reverse rule of 78? Thanks.
order 4+ determinants 1999-12-06
From Joe Kron:
Why is it never shown how to calculate the value of 4x4 (or larger size) deteminants by the diagonal multiply methods that are generally shown for 2x2 and 3x3 determinants? The method I'm talking about is called Cramer's Rule??? Is this method not extensible to order 4+ and if not why not? Anyway the method always shown for order 4+ is called "reduction by minors" which is not the answer to this question.
Camels and bananas 1999-12-02
From Marie Rich:
Corey Camel's harvest, worth its weight in gold, consists of 3000 bananas. The market place where the stash can be cashed in is 1000 miles away. However, Corey must walk to the market, and can only carry up to 1000 bananas at a time. Furthermore, being a camel, Corey eats one banana during each and every mile she walks (so Corey can never walk anywhere without bananas). How many bananas can Corey get to the market?
Area of a triangle from vertex coordinates 1999-04-21
From Mark Tyler:
I'm no schoolkid, but I liked your answers about triangles. You might enjoy a quick look at this, the kids may too.

I was working on a Voronoi dual where I had to calculate the areas of very many triangles expressed as vertex coordinates, so I derived the following very direct formula:

A = abs((x1-x2)*(y1-y3)-(y1-y2)*(x1-x3)) for triangle (x1,y1)(x2,y2)(x3,y3)

I've never seen this in a textbook. Is it original? I doubt it, the proof is only a few lines long.

Regardless, it may be fun for the kids, even if it's not on the curriculum.

Intersection of Planes 1998-12-03
From Lindsay Fear:
My name is Lindsay Fear. I am an OAC student (which is the Ontario equivalent to Grade 12 in most other states and provinces). I am in an Algebra and Geometry course and am currently studying a unit on equations of planes. Our teacher has given us this question that my friend and I have attempted several times, but we are still unable to solve it. My teacher has also suggested using the internet as a resource. The question is:

Prove that a necessary condition that the three planes

` -x + ay + bz = 0 ax -  y + cz = 0 bx + cy -  z = 0 `
have a line in common is that
a^2 + b^2 + c^2 + 2abc = 1

il y a deux contenant 2007-01-23
From Eric:
il y a deux contenant un de 3 litre et un de 5 litre les deux sont vide comment en les remplisant on peux obtenire 4 litre