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The discriminant |
2010-01-17 |
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From Sonjonnia:
What is the value of the discriminant?
16x^=16x-4
Answered by Penny Nom. |
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A push-button padlock |
2010-01-17 |
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From Vince:
Hi,
I have a push-button padlock using ten buttons (1-2-3-4-5-6-7-8-9-0).
Five digits must be pushed in order to open the lock.
Each digit can only be used once.
Order is not supposed to matter.
How many different possible combinations? And what are they?
Answered by Harley Weston. |
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A linear equation with the variable on both sides |
2010-01-16 |
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From dog:
4x-9=7x+12
Answered by Penny Nom. |
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Cubic feet |
2010-01-16 |
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From deb:
1 room 49x24 1 room 18x18 need 6 inch deep can u convert to cubic feet for me thank you
Answered by Penny Nom. |
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The adjacency matrix of an undirected graph |
2010-01-15 |
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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
Answered by Robert Dawson. |
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Probability, counting and cards |
2010-01-15 |
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From Julie:
Hello,
- Select a card from the deck(card deck of 52 cards). Place the card back in the deck. What is the probability that both cards will be black? Is it 25/104, 24%?
- Select a card from the deck. Do not replace the card. Select another card. What is the probability that a red and a face card are the two cards you selected? Is it 2/221, .9%?
- Remove the red cards from the deck and assume that the remaining cards have been shuffled: select a card from the remaining deck. Place the card back in the deck. Select another card. What is the probability that both cards will be black? Is it 26/26 x 26/26= 1 x 1 = 1 , 100%?
Select a card from the remaining deck. Do not replace the card. Select another card. What is the probability that a red 3 and a face card are the 2 cards you selected? Is it 0/26 x 6/26 = 0, 0%?
- Seperate 12 face cards from the rest of the deck. Assume that the face cards have been shsuffled. Select 3 cards from the pile of face cards. How many different arrangements can be made by selecting 1 of each card (jack, king, queen) from the pile? is it 1/4 x 1/4 x 1/4 x 1/4 = 1/64?
- How many different ways are there of selecting the queen of clubs, then the king of diamonds, and then the jack of hearts from the pile? Is it 1/12 x 1/12 x 1/12 = 1/1728?
Answered by Robert Dawson. |
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soustraction |
2010-01-14 |
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From LUCAS:
comment faire l'operation suivant car je ne me souvient plus tres bien
D'avance merci
4h44mn53s-2h52mn45s
Answered by Pierre-Louis Gagnon et Claude Tardif. |
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A schedule for a pool tournament |
2010-01-14 |
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From john:
I need to know how to set up a pool tournament 12-14 players playing once a week, either 10-12 weeks whichever works out the best, what players would play what players week one through week ten or twelve? I hope you can help, I cant figure out the formula.
thanks
John
Answered by Victoria West. |
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A circular photo in an octagonal frame |
2010-01-13 |
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From Mike:
I have a circle photo 18 and one quarter inches round. I want to cut frame for it in a octagon shape. What would the angle and the length of cut be?
Mike
Answered by Robert Dawson. |
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A triangular prism |
2010-01-13 |
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From Breon:
what is the formula for a triangular prism?
Answered by Robert Dawson. |
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Trigonometry and picture hanging |
2010-01-13 |
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From george:
The top of a picture 1m high 0.8m from the ceiling. At a point on the ceiling directly in front of the picture, we wish to install a light so that the angle subtended by the picture equals to the angle of depression of the top of the picture. How far out from the wall should the light be installed?
Answered by Penny Nom. |
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Mixed numbers |
2010-01-13 |
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From Linh:
Perform the indicated operations:
6 1/4 + (- 2/3) x 1 1/2
Answered by Penny Nom. |
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What percentage am I reducing it by? |
2010-01-13 |
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From Lynda:
I need to calculate the percentage of a total number.
If my total is 2.9 million and I take out 187,000 what percentage am I reduing it by?
Answered by Penny Nom. |
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Related Rates Problem |
2010-01-12 |
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From Neven:
A woman raises a bucket of cement to a platform 40 ft
above her head by means of a rope 80 ft long that passes
over a pulley on the platform. If she holds her end of
the rope firmly at head level and walks away at 5ft/s,
how fast is the bucket rising when she is 30 ft away
from the spot directly below the pulley?
(G. F. Simmons, Calculus with Analytic Geometry, pg.142)
Answered by Penny Nom. |
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A proof by induction |
2010-01-12 |
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From Bhavya:
Prove by induction that if Xi >= 0 for all i, then
(Summation Xi from 1 to n)^2 >= Summation Xi^2 from 1 to n
Answered by Penny Nom. |
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