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n log n = 36 * 10 ^ 12 |
2013-11-12 |
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From shihab:
How to find value of n in this equation :
n log n = 36 * 10 ^ 12
Answered by Penny Nom. |
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One train overtaking another |
2013-11-11 |
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From kiran:
two trains of equal length are running in parallel tracks in the same direction with the speed of 60km/hr and 90km/hr respectively the latter completely crosses the former in 30 seconds the length of each train is in mtr
Answered by Penny Nom. |
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Matrices |
2013-11-10 |
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From Ricky:
Why must we have brackets around matrices. Why don't we just neatly write an array of entries cross-wise and up and down to indicate a particular matrix?
Answered by Chris Fisher. |
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A lever |
2013-11-09 |
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From Durgesh:
A farmer uses a 2 m long lever to lift large rocks from the ground of his field . He places a fulcrum 20cm from the rock end of the lever and then stands on the other end, levering out the rock. If the farmer weighs 100 kg , what is the heaviest mass of the ro ck that he can lift using this method? (how to solve)
Answered by Penny Nom. |
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The popcorn box problem |
2013-11-07 |
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From Dave:
We know that calculus can be used to maximise the volume of the tray created when cutting squares from 4-corners of a sheet of card and then folding up.
What I want is to find the sizes of card that lead to integer solutions for the size of the cut-out, the paper size must also be integer. EG 14,32 cutout 3 maximises volume as does 13,48 cutout 3.
I have done this in Excel but would like a general solution and one that does not involve multiples of the first occurence, as 16, 10 cutout 2 is a multiple of 8,5 cutout 1.
Answered by Walter Whiteley. |
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200,000 cubic metres |
2013-11-06 |
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From John:
Hello:
I'm a journalist reporting on the proposal to bury 200,000 cubic metres of radioactive waste below ground near Kincardine, Ontario. I'm trying to put this figure into some kind of perspective for readers -- particularly in the U.S., where most are unfamiliar with the metric system. I don't know whether there's any particular frame of reference that would be enlightening -- U.S. football fields, Olympic-sized swimming pools, etc. Can you help? Thanks very much in advance, John
Answered by Harley Weston. |
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The average time per mile for a marathoner |
2013-11-04 |
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From Peter:
a runner ran a 26.2 mile marathon in 2hours 8minutes and 24secounds. the question is, what was his average time for each mile that he ran?
Answered by Penny Nom. |
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Substitution type simultaneous equations |
2013-11-03 |
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From Kayla:
I am having problems with substitution type simultaneous equations, when the variable you are substituting is a algebraic one:
y=x^2-3x+4 and 3x-2y=1
I have rearranged 3x-2y=1 to get x=(1+2y)/3 but when I substitute this x value into the other equation, I get the wrong answers!
Would appreciate any help! Thank you.
Answered by Penny Nom. |
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Water flowing out of a tank |
2013-11-03 |
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From Carolyn:
The flow of water out of a hole in a tank is known to be proportional to the square root of the height of water above the hole.
That is,
dV/dt (proportional to) sq root (h)
The tank has a constant cross-sectional area A, show that the height of water in the tank is given by
h = ((-kt+C)/2)^2
If the tank is 9 metres high, and it takes 5 hours for it to drain from full to half full,
how much longer will we have to wait until it is completely empty?
Answered by Penny Nom. |
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The depth of a lot |
2013-11-02 |
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From Gini:
what is the depth of a lot with 45 feet frontage containing 1080 sq yards
Answered by Penny Nom. |
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A ratio problem |
2013-10-31 |
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From indu:
students of a school have been into 2 groups in the ratio 6:11, if the group has 870 students, how many students are there in all the school?
Answered by Penny Nom. |
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An extension using concrete blocks |
2013-10-30 |
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From david:
hi how many concrete blocks would i need for an extension 50 ft long ,20 ft wide and 12ft height
Answered by Penny Nom. |
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A sloped concrete wall |
2013-10-30 |
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From Brad:
We are planning on pouring concrete in a wall form that is sloped. One end is 73 inches tall, and it tapers to 24 inches tall over a distance of 348 inches. It is flat on bottom and sides and is 12 inches thick. Thanks.
Answered by Penny Nom. |
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Is-5/-11 a positive rational number? |
2013-10-30 |
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From tazneem:
Is-5/-11 a positive rational number
Answered by Penny Nom. |
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A plane |
2013-10-27 |
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From Thomas:
Why is this 3d plane flat?
if m ≠ n
arcsin(sin(m*arctan(x/y))), arcsin(cos(n*arctan(x/y))),
Pi-arcsin(sin(m*arctan(x/y)))-arcsin(cos(n*arctan(x/y)))
This is using radians.
These are angles of a triangle, when m and n are the same it is a right triangle. All three inputs are not equal to each other. The last input is pi minus the first two inputs, which makes a complete triangle.
I was kind of hoping to find more lissajous curves. It doesn't make sense to me that this is a flat plane, a diagonal one at that.
I'm not a student or anything. I'm just wasting time.
Answered by Chris Fisher. |
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