Tuesday
July 7, 2015

Posts by MathMate


Total # Posts: 11,301

math
Lateral surface of a cylinder Al=2πr*h where h is measured along the axis of the cylinder. When the rectangle is rotated along it's length, then h=length, r=width. When the rectangle is rotated along it's width, then h=width, r=lengh. So you can calculate the ...
July 21, 2013

Math<Please Help>
Simple way: Multiply the planar area (25m*12m) by the average depth of (1+4)/2=2.5m to get volume= 750 m³. Calculate the area of the trapezoid which is obtained by cutting a vertical section along the length: 25*(1+4)/2. Multiply the above by the width of 12 m to get the ...
July 21, 2013

Math
Computers actually use binary number systems, since a switch can either be on or off. However, contents of computer memory is more concisely represented by octal and hexadecimal representations because 1. they are easy to convert to and from binary system 2. they are condensed...
July 21, 2013

GCSE Physics
Energy paid for =30/0.15=200 KWH Number of hours for boiler = 200 KWH / power of boiler The number of hours will not be know until the power of the boiler is known.
July 20, 2013

math
Q4c: 1/x^2*x*sqrt(x)*sqrt(sqrt(x))=a^c; 1/x^(1/4) = a^c x=a^(-4c) For: log5(5-4x)=log√5(2-x) log5(5-4x)=log5(2-x)² 5-4x=(2-x)² x=±1
July 20, 2013

physics
Volume of liquid =3.57*10^-4 m^3 =357 ml mass of liquid =357 g mass of aluminium (can) =421-357 =64 g density of aluminium = 2.7 g/ml Volume of aluminium = 64/2.7 cc = 23.7 cc
July 20, 2013

geometry
I am sorry about the incorrect designations. However, the same process can be used to solve for CP=3, although the result would be different. It seems to me that Steve's method is simpler, so use his method. Using Newton's method to solve for a non-linear equation f(x...
July 20, 2013

geometry
First draw the square ABCD and indicate a point P inside the square near the side AB about 1/3 from A to B. Label the lengths AP=1, PB=2, PD=3, and each side of the square s. Join BD and mark the length (√2)s. Label ∠APB as α, ∠DPA as β. Consider each ...
July 20, 2013

Statistics
The following reference may confirm your assumptions. http://cjasn.asnjournals.org/content/3/5/1246.full
July 19, 2013

MAT LAB
For 9_3, the question is not clear because we do not see the accompanying figure. However, on examining the data, it seems probable that the two "walls" (meaning no strain/movement along that direction) are in the y-direction, which means that εy=0. From the ...
July 19, 2013

MAT LAB
Note: Equations (A), (B) and (C) may be used to solve problem 9_2_1, namely Lx=L(1+εx),... Watch the signs of the stresses.
July 19, 2013

MAT LAB
Note that 1/20 is a relatively large strain and the above equations are approximate to first order and may not be accurate for large strains. Use the relations: εx=[σx-ν(σy+σz)]/E ....(A) εy=[σy-ν(&sigmaz;+σx)]/E ....(B) &...
July 19, 2013

MAT LAB
9_1_1 Recall that for an isotropic material, when σx is applied on a material of modulus of elasticity E, then the strains are: εx=σx/E from which e can be calculated. Since εy=-νσx/E, and similarly εz=-νσx/E, we are able ...
July 19, 2013

Calculus
This is a project you need to do using Mathematica. I suggest you go ahead and actually learn to use Mathematica to solve the above problems. If you have doubts and would like to check you results, you are welcome to post them for a check here.
July 19, 2013

math
Yes, 2655 in³.
July 19, 2013

math
Calculate volume of locker V=L*W*H Calculate volume of books (given) B=1545 in³ Calculate volume left =V-B
July 19, 2013

Math
The volume to be integrated is bounded by the planes 0≤x≤2 0≤y≤2 z=0 and the surface z=16-x²-2y². Thus the volume is given by the triple integral: V=∫∫∫z dz dx dy Where z is evaluated from 0 to 16-x²-2y², x and y are both evaluated ...
July 19, 2013

math
The rule for converting from metres to centimetres is that one metre equals 100 centimetres.
July 18, 2013

Solution Set
{x+y=3 ............(1) {-3x+2y=-19 ...........(2) Solve by elimination. Multiply (1) by 3 and add to (2) in order to eliminate x: 3x+3y=9 ..........3(1) -3x+2y=-19 .......(2) Add together 0x+5y=-19+9=-10 Solve for y: y=-10/5 = -2
July 18, 2013

Calculus
If you need help with finding the standard forms of the particular solution, check your course notes, your textbook, or the following link: http://tutorial.math.lamar.edu/Classes/DE/UndeterminedCoefficients.aspx
July 18, 2013

Calculus-ODE
Start with solving for the complementary solution to the homogeneous equation 2y"+3y'+y=0, the characteristic equation is 2r²+3r+1=0 which is an algebraic equation which can be factorized into (2r+1)(r+1)=0 or r={-(1/2), -1} The complementary solution is ...
July 18, 2013

math
Proportions: 100% : 1.75 hours x% : 1 hour x=1*100%/1.75
July 16, 2013

math
Use time = 1/(1/M+1/R)
July 16, 2013

math
2=1/(1/6+1/B) => B=1/(1/2-1/6)=3
July 16, 2013

math
1/(1/20+1/30+1/10) =60/11 minutes
July 16, 2013

math
1/(1/6+1/5.5+1/2.2) =1.245 DAYS
July 16, 2013

algebra
√(75) =√(25*3) =√(5²*3) =5√3
July 16, 2013

math
2³=?
July 16, 2013

gen physics
The centre of gravity is located at a point such that the product of mass multiplied by the distance to the C.G. is equal, namely: Let x = distance from mA, then 50-x = distance from mB. mA*x = mB(50-x) solve for x, and hence 50-x.
July 16, 2013

gen physics
apparent ρ=7860-1000=6860 kg/m² Tension in wire =apparent weight =apparent mass*g =(0.154³)*6860*9.81 N =246 N (approx.)
July 16, 2013

physics
ω2=ω1)+angular acceleration*time or time = (ω2-ω1)/angular acceleration =(0.28-0)/0.021 =40/3 sec.
July 16, 2013

Math
Please comment on the previous answer before reposting: http://www.jiskha.com/display.cgi?id=1373921871
July 16, 2013

math :)
You're welcome. :) The method above is correct, but the final result should be 2 7/24 lbs, since 2*24=48, and 55-48=7. Sorry for the oversight.
July 16, 2013

math - addition of fractions
The question requires us to add three fractions, with different denominators. The first step is to find a common denominator which is the LCM (least common multiple) among 3,4 and 8. Since 4 divides 8, so 4 need not be accounted for. The LCM of 3 and 8 is just the product 24, ...
July 16, 2013

Geomtry
I have a different interpretation of the problem. If I were to assume "three sides" as one length (parallel to the canal) and the two other sides perpendicular to the canal, then we are only fencing three sides on land, and the fourth side is bounded by the canal. ...
July 16, 2013

math
240.75 is correct.
July 16, 2013

Math
From the knowledge of divisibility, we know that 2 is a factor (all even numbers). That reduces 2002=2*1001 Again, the difference of sums of alternate digits equals zero (1+0)-(0+1)=0, so it is divisible by 11. That makes 2002=2*11*91 We should (try to) know all prime ...
July 16, 2013

Math
She cannot subdivide the equilateral triangle into 2 isosceles triangles. This is the smallest N which is impossible. She can subdivide it into 3 congruent isosceles triangles by joining the centroid with each of the vertices. Each triangle is then 30-30-120 as angles. Each of...
July 15, 2013

Calculus
The idea is to find the family of lines perpendicular to L:7x+5y-2=0. Out of that, we find the particular line L1 passing through P(-6,-2). The intersection of L and L1 gives the required point (closest to P). Family of lines perpendicular to L passing through P0(x0,y0): L : ...
July 15, 2013

Statistics
With replacement, the probability of selecting a good apple stays at 60/80=3/4. For a two-step experiment, the probability is the product of individual steps, hence, probability of select a good apple in each pick is (3/4)^2=9/16
July 15, 2013

maths
Two trains with speeds s and s+5 km/hr. Initial distance=340 km final distance = 30 km Total distance travelled = 340-30=310 km Total speed = s+s+5=2s+5 Time = 2 hrs Form equation equating distance travelled Time*speed=distance, or 2(2s+5)=310 2s+5=155 2s=150 s=75 Speeds of ...
July 15, 2013

French
"J'ai faim" is the proper expression to say "I am hungry." Just like in English we would not say "I am hunger", it would be incorrect say the equivalent in French. Another notable difference in French from English is about age. We would say &...
July 15, 2013

object oriented programming
Can you show us your pseudocode as a start?
July 14, 2013

trig
Parentheses are assumed missing. Implied parentheses are ALWAYS required in numerator and denominator of fractions. (cos^2x+sin^2x)/(cot^2x-csc^2x) This problem can be solved by converting all functions in terms of sine and cosine according to the standard definitions. (cos^2x...
July 14, 2013

Java programming- simulation of rolling dice
You have made the arrays die1...die4 to do two things: 1. as a counter (accumulator) for the frequency, and 2. as the value of the face. This is an impossible task, and that explains why the total adds up to more than a million. I suggest you make the following changes: 1. Add...
July 14, 2013

Elementary mechanics
Use the kinematics equation: Vf=Vi+at where Vf=final velocity=i-2j (m/s) Vi=initial velocity, yet unknown a=acceleration=F/m (in vector form) t=time=10 s a=(2i+7j)/5=0.4i + 1.4j Vf=(i-2j)+(0.4i+1.4j)(10) =(i-2j)+(4i+14j) =5i+12j
July 14, 2013

Computers C++
What are your thoughts?
July 14, 2013

GEOMETRY (SA oftriangular pyramid)
In the calculations of surface area of a pyramid, the height is not required if the apothem (slant height) is given. The height is required, however, to calculate the volume of a pyramid. In fact, the height h is not consistent, because h should always be less than the slant ...
July 14, 2013

GEOMETRY (SA oftriangular pyramid)
Lateral surface area =perimeter of base * apothem /2 =3b*s/2 (for a regular pyramid with a triangular base) Area of triangular base with side b =(√3)*b/2*(b/2) =(√3)b²/4
July 14, 2013

math:units conversion
Convert 6 cm to mm = 60 mm. Now add 60mm to 4 mm to get your answer.
July 14, 2013

Math
If each team plays with each of the other four teams N times, then the number of games played would be: 4, 8, 12, ... Can you find which of the five numbers does not belong?
July 13, 2013

College Algebra
Start with (x-(-1/6))(x-(-8/9))=0 Multiply by 54 on both sides to get (6x+1)(9x+8)=0
July 13, 2013

trig
Convert all three functions in terms of sine and cosine, hence simplify.
July 13, 2013

statistics
Possible typo in bold: "Playing game of chance and pay 300 by rolling a fair die one time if you rome a 2 and receive $1300 if you roll a 4 or six you receive $900 if you ore a 3 5 or one receive nothing. find expected value for this game. based on value is it a good game...
July 13, 2013

statistics
Binomial distribution: - large population=>probability is (almost) constant - p=0.5 (men) q=(1-0.5) (women) - random independent multiple trials N=9 - 2 possible outcomes at each trial P(7)=C(9,7)*p^7 * q^2 =(9!/(2!7!))*0.5^7*(1-0.5)^2 =0.07 (approximately)
July 13, 2013

Calculus
See: http://www.jiskha.com/display.cgi?id=1373656357
July 12, 2013

Linear Equation
Let x=number of gallons of regular sold then 220-x=number of gallons of premium sold Total receipt: 2.20x+2.70(220-x)=519 Solve for x.
July 12, 2013

Math :)
You're welcome!
July 12, 2013

Math
x=(5±(√15)*i)/2 If you do not expect complex roots, please check for typos in the original question.
July 12, 2013

Math
x/(x-2) + (2x)/[4-(x^2)] = 5/(x+2) This calls for finding the common denominator, and then solving for x using the numerators. Do not forget to exclude the asymptotes values of x where the denominator becomes zero. LCM (lowest ommon multiple) of denominators (x-2), (4-x²...
July 12, 2013

algebra1 HELP PLEASE Thanks you!!
y=√(64*25)=√(40²)=40 f.p.s.
July 12, 2013

algebra1 HELP PLEASE Thanks you!!
Not sure if there is a typo in your question, the speed is y(x)=5√(x)=5√(25)=25 This corresponding an equivalent acceleration approximately that of Mars.
July 12, 2013

maths
18+0.5+2.5=?
July 12, 2013

maths
The idea is to convert f(x)=asin(x)+bcos(x) into the form g(x)=k*cos(a+φ) where k and φ are constants dependent on a and b. This way, it is easy to show that the max/min values of the f(x) is ±k. Start with expanding g(x) using compound angles. g(x) =k(cos(&phi...
July 12, 2013

Maths
See: http://www.jiskha.com/display.cgi?id=1373620166
July 12, 2013

Math
First find the rule of the parabola: We know that the parabola curves (is open) towards the bottom, so the rule is y(x)=b-ax² if we set the y-axis to cut the vertex. Since y(0)=16=b, so b=16 or y(x)=16-kx² Also, y(4)=0 tells us that k=1, or the rule of the doorway is...
July 11, 2013

alg2 check?
Remember that ^ has higher precedence than * or +, so in these expressions, parentheses are required: 1. (2)(3)x^(1+3) =6x^4 2. (4)^3 x^(1*3) y^(2*3) =64 x^3 y^6
July 11, 2013

Math.
Two step experiment: multiply the probability of each step. A. P(Jeans,t-shirt)=0.3*0.6=0.18 B. P(jeans, ~t-shirt)=0.3*(1-0.6)=0.12
July 11, 2013

Math- important!!!
Use binomial distribution, p=0.28, q=(1-0.28)=0.72 A) n=5 P(3/5)+P(4/5)+P(5/5) =3C5*p^3*q^2 + 4C5*p^4*q^1 + 5C5*p^5*q^0 =10(0.28^3)(0.72^2) + 5(0.28^4)(0.72) + 1(0.28^5)(0.72^0) Use your calculator to find the answer for (A) B) Expected value for binomial distribution with n=...
July 11, 2013

physics
150 * 2*3600 j + 250 * 10*60 j =1230000 j =1.23 Mj
July 10, 2013

differential calculus
Intuitively, the circle has a bigger area for the same circumference, so we try to make a bigger circle. Also, since the area increases as the square of the circumference, we want to make 1 single shape as opposed to two. So intuitive answer is to make the smallest square ...
July 10, 2013

French
Each country name has a gender and a number. The country France is feminine singular, as demonstrated by the phrase "Vive la France!" The country United States (Les États-Unis) is masculine plural. For feminine country names, we use the preposition "en&...
July 9, 2013

math
The question does not give the required context. Some countries charge sales tax on labour, and some may not. I believe Overhead rate would be added to the labour, meaning that for every $12 paid to the worker, the customer pays $12(labour)+$15(overhead)=27. If sales tax does ...
July 9, 2013

Computer Programming
Your code seems to be in reasonable shape, except that it does not yet implement the algorithm to find the maximum revenue. So the current revenue is 600*50=30,000$ a month. Your program will increase the rent by $40 steps and recalculate the revenue. When the revenue starts ...
July 9, 2013

MATH:( Base systems?!
Divide the number by the base and note the remainder on the right. The digits from bottom to top is the number required. Example: Find 37 to base 5. 37 R 2 (37/5=7 R2) 7 R 2 (7/5=1 R2) 1 So the number is 1225
July 9, 2013

Number and Operations
3,6,9 and 18, since 20/18 also has a remainder of 2.
July 9, 2013

math
The question should have read: There are 35 students in a class who stu dy either art, music or both. 15 study art. Twice as many students who study art study music. COMPLETE THE VENN DIAGRAM TO SHOW. 35 students in all 15 study art 2*15=30 study music so 35-30=5 study only ...
July 9, 2013

Math 17 Synthetic Division
Showing steps of synthetic division requires lining up many numbers vertically, which is impossible to do at this web site. I suggest you refer to examples of sites which can format number displays. Try for example: http://www.purplemath.com/modules/synthdiv.htm
July 9, 2013

GEOMETRY LATERAL AND SURFACE URGENT (PLEASEHELP)
Total surface area of a rectangular box =2(lw+wh+hl) where l,w,h=length, width and height respectively. Total surface area of a cubical box (all sides equal to "a" =6a² Total surface area of a Rectangular prism : see above for rectangular box
July 9, 2013

Math
solid: square pyramid height, h = 15 side of base, s = 5 Area of base, Ab=5^2 area of cross section at height y =Ab*(y/15)^2 Volume (using the general solid integral formula based on Simpson's rule) V=(Area at top + Area at base + 4*area at mid-height)*height/6 =(0+25+4*6....
July 9, 2013

Prisms
See: http://www.jiskha.com/display.cgi?id=1374407375
July 9, 2013

Number System
Subtraction is done as in decimal, one digit at a time from the right. Borrow from the left digit if necessary. If the result is expected to be negative, reverse the subtraction (to get a positive difference) and then change the sign. Example: 1101 -0110 ----- 0111
July 9, 2013

Number System
Not sure if the question was quoted properly, because the last group of the first number has only three digits. To add two binary numbers, we add a digit at a time just like in decimal, using the following rule: 0+0=0 0+1=1 1+0=1 1+1=0 with a carry of 1 So to add 101 to 111 we...
July 9, 2013

Number System
You can convert too hex from binary by grouping, from the right, four digits at a time: 1 1011 1011 and convert each group from binary to a decimal digit, using A for 10, B for 11...and F for 15. For example, 1011=> 8+0+2+1=11=>B so the above example becomes 1BB in hex.
July 9, 2013

Computer Programming
I suggest you give it a try and post any difficulties you encounter. Programming is not as hard as it seems once you get started.
July 8, 2013

Math
Width = x inches (given) Length = 2x inches(given) Height = 5 inches (given) Volume = 5*x*2x = 10x² in.3
July 8, 2013

Math (please help me Steve)
Here's a lower bound solution. You may want to investigate other possibilities. The number 7 can be partitioned into 3 ascending non-negative integers in 8 ways, namely: 007# 016 025 034 115# 124 133# 233# There are 3 permutations of partitions (indicated #) with non-...
July 8, 2013

Math
Both, in a minute and in an hour. The LCM of 3, 5 and 10 is the same as the LCM of 3 and 10 because 5 divides 10 (5 is a factor of 10). The LCM of 3 and 10 is 30. So the soonest the will flash together is 30 seconds.
July 8, 2013

Vba
First, the concept of sub programs is to isolate a particular calculation and make a "black box" which returns a "complicated" answer without having to worry about how it is done. On the other hand, the UI (user-interface) belongs to a separate element of ...
July 8, 2013

math
15 2's = one way 10 2's + 2 5's = 12!/(10!2!) ways 5 2's + 4 5's = 9!/(5!4!) ways 6 5's = one way Total=194
July 7, 2013

Calculus
Think of f(x)=f1(x)+f2(x) where f1(x)=x f2(x)=-cos(x) We note that f1(x) is monotonically increasing throughout [-π, π) while f2(x) is increasing between [-π, 0) and decreasing between [0,π). Therefore to find the absolute maximum and minimum, we only need to check...
July 7, 2013

Statistics/Probability
The sum P(RR)+P(PP)+P(SS)=0.3288 which rounds to 0.33.
July 7, 2013

Statistics/Probability
A is correct. I assume you know that rock wins over scissors, paper wins over rock, and scissors wins over paper. For the other parts, make a tree diagram complete with corresponding probabilities and sum all the appropriate outcomes to get the probability. Example: R=rock, P=...
July 7, 2013

math
Let x=length of one of the equal sides. Then 42=16+x+x Solve for x.
July 7, 2013

Math
Z1=(2-5.5)/3.5=-1 Z2=(9-5.5)/3.5=+1 Look up the normal distribution table to find P(Z1<Z<Z2)
July 7, 2013

physics
Wavelength = Speed/frequency Speed of light: 3*10^8 m/s Frequency = 3*10^9 Hz Wavelength = 3*10^8/(3*10^9) = 0.1 m = 10cm
July 7, 2013

heeeeeelp math
Not too sure the point of the question, but here's the answer anyway, assuming b and c are given but unknown constants. To find (max|f(x)|) for x∈[-10,10]: Complete squares to get f(x)=(x+b/2)²+c-b²/4 where (-b/2, c-b²/4) is the vertex. If -b/2 ∈...
July 7, 2013

heeeeeelpm math
Continued from http://www.jiskha.com/display.cgi?id=1373027417 Can you show an idea of your probability tree to make sure that your interpretation corresponds to what was asked? What did you get for your answer?
July 7, 2013

(pls help) physics
Q1 1kg = 1000 g It does not make sense to use a bucket of 1.5kg to pull up 10 g of water. You must mean 10 kg of water. 1.5kg+10kg=11.5 kg Work done = mgh (in consistent units) =11.5*9.8*8 j Q2 The word "average" has been used very vaguely. If it means to calculate ...
July 7, 2013

physics
Displacement = "distance" due north (requires speed and direction)
July 7, 2013

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