Saturday
December 20, 2014

Posts by MathMate


Total # Posts: 10,866

Trig
Use: cot(θ)=cos(θ)/sin(θ) sin²(θ)+cos²(θ)=1
May 7, 2014

chemistry
C1V1=C2V2 (a) 1.0 mol/L * 0.2L = C2 * 1.0 L Solve for C2 (b) C2 (from a) * 25 cm³ = (1.6 mol/L)*V2 Solve for V2.
May 7, 2014

Physics
Calculat the distance d (metres) it hits the ground when there is no wall. Use reflection to calculate the bounce off the wall. Then case 1: if d>10 m. Ball hits ground at (d-10) before the wall. case 2: if d<10 m. Ball hits ground at d m. from the girl.
May 7, 2014

Java
This is different from public, or private. Sometimes it is call package or default access. Read up at: http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html
May 7, 2014

physics
use mv²/r = mg solve for v.
May 6, 2014

Data Structure
Assume the boat and the boys are on the same side of the river at the start and finish. To get one villager across, the two boys must row over, leave a boy on the other side, row back alone, let a villager row over, then then boy on the other side will bring the boat back, ...
May 6, 2014

chemistry: please check work
Procedure should be correct, did not check the calculations.
May 5, 2014

math
If the assumption is that the population growth is constant at 4.5%, then Let x=population in 2000, 8791894=x*1.04510 Solve for x.
May 5, 2014

Math
transpose terms to the form y=ax+b, then a is the slope and b is the y-intercept. 6x=y+1 becomes y=6x-1, compare with y=ax+b and find what a (slope) and b (y-intercept) are.
May 5, 2014

algebra
Translating in English, you have defined a universal set of integers from one to ten. Then you defined sets (presumably belong to the universal set) which combine ("unioned") to form a new set. The first, {x|x is multiple of 2} means the set of even numbers between 1...
May 5, 2014

chemistry
Use: C1V1=C2V2 Measure all concentrations in mol/dm^3, and volumes in dm^3 2.0*V = 0.5*2.5 V=1.25/2=0.625 dm^3 or, approximately, 0.63 dm^3 rounded to 2 significant figures.
May 5, 2014

Programming
Do you need help with the flow-chart, algorithm, the coding or debugging? It would be best for you to tell us what you have learned, and what you have done so far.
May 5, 2014

math mrs. sue HELP!!!
Say you have a data set {4,6,8,9,10} 1. Find the mean = (4+6+8+9+10)/5=7.4 2. Sum the deviations from the mean (absolute values, no negatives) |(4-7.4)|+|(6-7.4)|+|(8-7.4)|+|(9-7.4)|+|(10-7.4)| = 9.6 3. Divide the sum by the number of data (n=5) to get 9.6/5=1.92 4. 1.92 is ...
May 4, 2014

Math
Use comparison method: 6-x=y=x-2 means 6-x=x-2 Solve for x and substitute into the original equations to solve for y.
May 4, 2014

math
Your work is correct, but probably made some mistake with the calculator. Volume = πr²h*1.06 = π(51)^2(120)×1.06; =330847.2π =1039387.133 mm³ approximately.
May 4, 2014

engineering
For the experiments to verify water-cement ratio, go with Bob Pursley's idea. Water is necessary for the concrete to set, but too much water will weaken the concrete. Too little will make it unworkable, and will end up having voids. Plastisizers are usually added to ...
May 4, 2014

Science
Weight = total air resistance, so by Newton's first law, the skydiver free-falls at uniform (terminal) velocity.
May 4, 2014

Algebra 2
Games are random processes. All we can say is that if he wins, he gets one point, and if he loses, he loses one point. We also know (or believe) that the probability of winning or losing is each 50%. The actual outcomes depends naturally on chance. But in the long run, the ...
May 4, 2014

Algebra 2
oops The probability on the second line should read 0.5 (not negative).
May 4, 2014

Algebra 2
Find probability of numbers matching (2/4) and not matching (2/4). Construct table for A: Outcome value,x P(outcome) x.P(x) Win..... +1 ...... 0.5 ....... 0.5 Lose.....-1 ...... -0.5 .......-0.5 Sum(x.P(x))=0, so game is fair.
May 4, 2014

Chemistry
Let K=[HI]²/([H2][I2]) The given reaction is in equilibrium at 430°C, if K=Kc=54.3 Substitute given concentrations to get K=[HI]²/([H2][I2]) =0.5²/(1*1) =0.25 < 54.3 Therefore the reaction is not in equilibrium and will proceed in the forward direction ...
May 4, 2014

Algebra
Divide each term of the numerator by 2m^3: -6m^9/(2m^3) = -3m^6 -6m^8/(2m^3) = -3m^5 -16m^6/(2m^3) = -8m^3 Choose your answer accordingly.
May 4, 2014

Precalculus
Yes, the square bracket means the value is included in the interval, and ( or ) means excluded. There are other notations where ( or ) is replaced by a square bracket pointing outwards, for example, [0,2π) is the same as [0,2π[ To solve the above problem: cos^2x=2+2sinx ...
May 4, 2014

Geometry
π is equivalent to 180° So 7π/4=7*180/4=315°
May 4, 2014

Trignometry
Since it is a rational number, the numerator and denominator can be replaced by integers. Using (b), you can create any integer, and using (a), you can divide the two numbers, which means you can create any rational number. Hope that helps.
May 4, 2014

Trignometry
Assuming (c) is the equivalent of the original question: "given any positive rational number q, show that pressing some finite sequence of buttons will yield q" then we need a transformation from q -> q using the given functions. We look for mapping R to R, or ...
May 4, 2014

Math
The important term to consider is 60(1/3)^t, which has a domain of R (all real) and a range of (0,+∞). Therefore dom T(t) = R ran T(t) = (10,∞)
May 4, 2014

Math
The model is an exponential function such that e^rt=(1/2) where t=14 hours. e^(14r)=1/2 14r=ln(1/2) r=ln(1/2) / 14 =-.04951 (approx). In 22 hours, factor=e^(-0.04951*22) =0.336475 approx.
December 14, 2013

math
Step 1: Define variables: c=number of cars t=number of trucks "a dealer has 30 cars and trucks" translates to c+t=30 which means t=30-c .....(1) "If 2 more cars are delivered, the dealer will have 3 times as many cars as trucks." translates to c+2=3t .....(...
December 14, 2013

Math - Trig
Assume the observations were made from the same building. Let the distance of the building from the tree is D in m. Then D(tan22+tan50)=150 D=(150)/(tan22+tan50)
December 14, 2013

CHIMIE - English translation of question.
90 mL of 1.5N BaSO4 is mixed with 75 mL of 0.6M Na2SO4. 1. Calculate the ionic force of the resulting salt solution. 2. Deduce the value of the activity coefficient of Na+. Thank you. Rahil: SVP vérifiez si les valeurs sont bien 1,5N et 0,6M (surtout le mélange ...
December 14, 2013

SAT Math
An example problem could be: between 1 and 1000, how many numbers are neither divisible by 2 nor by 3. So from 1 to 1000, 500 numbers are divisible by 2 (even numbers), and from 1 to 999, there are 333 numbers divisible by 3. However, between 1 and 996 (next number is 1002)...
December 7, 2013

physics
It depends on the speed of the plane if the frame of reference is terrestrial, namely if the object is considered stationary on firm ground. If the frame of reference is the airplane itself, which cruises at a constant speed in rectilinear motion relative to the terrestrial ...
November 29, 2013

MATHS
If you are working on number theory, look up Chinese remainder theorem. If you have a puzzle or problem to solve, you can do it as follows: If we took one apple from the box, then the number of apples must be divisible by 2, 3, 4, 5, and 6. Therefore the number of apples would...
November 27, 2013

german
I do not speak German, but the little I know tells me that the "other" verb is placed at the end of the sentence, such as: Ich muss dort Deutsch sprechen. There I must speak German. One of our math teachers speaks fluently German. Hope he can give you a more detailed...
November 27, 2013

math
Bill amount * (1-0.03) to give the discounted amount, then add 6% tax Bill amount * (1-0.03) * (1+0.06) For $26.14, the final amount comes to $26.88, after rounding.
November 27, 2013

trig.
The tree top is 100*tan(52) feet higher than the person's eyes. To get the height h, above ground, h=100tan(52)+5 feet = 133 feet, approximately
November 27, 2013

Physic: Projectile Motion
let α be the angle of the projectile with the horizontal as it leaves the muzzle. Here α=0 degree. Let vi=initial muzzle velocity, then horizontal velocity, vh=vi*cos(α). Time taken to reach the target t=Horizontal distance/vh where horizontal distance = 100m...
November 26, 2013

Math
To find the x-intercept, let y=0 and solve for x in 3x=12, or x=4. So the ordered pair would be (4,0). Follow similar rules for the y-intercept.
November 18, 2013

math urgent
Use your calculator to find 26×56. Since they are both raised to the 6th power, if you are interested in mental calculations, you can apply the law of exponents and multiply the two bases before raising to the given power.
November 17, 2013

algebra
There are two equations with one unknown, and the two possible solutions are inconsistent.
November 17, 2013

math check
69 is correct!
November 17, 2013

math - Wish you luck!
:)
November 17, 2013

chemistry
M*V=2.01*711/1000
November 17, 2013

Calculus - Optimization
Good catch, Steve. Thank you.
November 16, 2013

Calculus - Optimization
Let the size of the square (cross-section) be s. Then we need to maximize V=s²(24-2s) with respect to s. First find the derivative and equate to zero: dV/ds = 48s-6s²=0 means s=0 or s=8 s=0 corresponds to a minimum volume and s=8 corresponds to a maximum volume. So ...
November 16, 2013

Business Math
Principal, P = $10000 interest per period of 6 months, i = 0.06 number of periods, n = 5 yrs/0.5 yr = 10 Value at maturity =P(1+i)^n He will have money to pay for the Jeep, and perhaps the sales taxes as well.
November 10, 2013

Math
7×6=42 7×7=49 so there are 6 and (48-42)=6/7 apples, or 6 6/7 apples.
October 15, 2013

Homework Help Calculus
Problem of units conversion. 0.4071504079 m³ =0.4071504079×10^6 cm³ =407150 cm³ approximately.
October 15, 2013

Algebra 2
The first equation has a y-intercept of -17. The x-intercept is -17/7=-(2+3/7) =-2.4286 approx. The second equation has a y-intercept of -2.4, and x-intercept of -2.4/(-0.3)=8. If you produce the two lines to intersection, the estimated solution would be (-2, -3)
October 15, 2013

Practice Exam Calculus
you can use the same approach as for the paint on sphere. A=4πr² dA/dr=8πr ΔA=8πr Δr =8π(20)(1/5) =32π
October 15, 2013

Math
If you mean (4/8)y - 21 = 3 then y=48 as you got. If the question were (4/8)y-21=0 then y=42
September 23, 2013

Chemistry
MC12H22O11=342 MCO2=44 C12H22O11+xO2=12CO2+... Ratio of mass of C12H22O11 to CO2 =342:12*44 =342:484 Mass of C12H22O11 that produces 3.6g CO2 =3.6*(342/484) =2.544g Mass ratio NaCl:C12H22O11 =(5.5-2.544):2.544 =2.956:2.544 Calculate mass percentage and reduce to 3 significant ...
September 23, 2013

geometry
The question defined what complementary angles are, but did not say that a and b are complementary. The question has a solution if a and b are complementary, and will be assumed as follows. if a and b are complementary, then a+b=90 angle a is 21 degrees more than twice angle b...
September 21, 2013

Surveying
Are you measuring the vertical angle (from the horizon) where 90 degrees is vertically up, or the zenith angle (from zenith, vertically up) where 91 degrees is just below the horizon? A vertical angle of 91 degrees requires a special eye-piece/prism, and is past the vertical...
September 21, 2013

math
There are 9 choices for each of the first three digits, and 25 choices for the last two digits. Use the multiplication rule to get: 93252
September 20, 2013

statistics
Use a probability tree: Next person male: 42% wash his hands: 43% female: 58% wash her hands 66% P(wash)=42%*43% + 58%*66% =0.5634
September 20, 2013

chemistry
When heated: 1. acetic acid phase change 2. sodium bicarbonate decomposition into sodium carbonate, carbon dioxide and water. 3. arsenic trioxide phase change
September 7, 2013

Chemistry
First establish the combustion equation and have it balanced: C8H18 + O2 -> 8CO2 + 9H2O. Balances for C, but not for O. Since there are 16+9=25O on the right, we need to double the number to make the number of molecules on the left a whole number. So it becomes: 2C8H18 + ...
September 7, 2013

physics
Hydrostatic pressure p varies linearly with height h, i.e. p=ρgh For a height of H and width of W, total force, F = W∫ρgh dh =ρgH²W/2 Ensure that all values are in SI units.
September 7, 2013

math
Trade discounts are successive discounts. The net price factor is equivalent to the net price of a $1 list price. Thus $1*(1-0.25)(1-0.15)(1-0.10) =0.57375 Use this factor to calculate the net price of $800 list.
September 6, 2013

geometry
I was thinking of something along the same lines, but couldn't find a good way to put it in action. Thank you for sharing the bright idea.
September 1, 2013

physics
Make a free body diagram of the staging. Sum forces acting on the staging, and the total should be zero. Upward (reaction) forces=660+410=1070 N Downward forces = 620 N + W Sum to zero 620+W=660+410 W=660+410-620 =450 N.
September 1, 2013

maths
Set up a system of equations: Let W=width L=length then Perimeter = 54 = 2(L+W) ...(1) L=2W-3 ...(2) Solve W by substituting (2) in (1), and hence solve for L.
September 1, 2013

math
Trade discounts are calculated successively. Thus for a list price of $1000, net price = $1000(1-0.3)(1-0.35)(1-0.2) = $364 Thus the trade discount amount (for a list price of 1000) is 1000-364=$636. For the list price of $29000, follow the same procedure.
August 24, 2013

GEOMETRY (Angles) PLEASE
You'd have to set up equations. First, let a=angle A, b=angle B and c=angle C, all in degrees. (Note: in solving math problems, it is important to define all symbols/variables used, including the units). We are given: "angle b is 5 more than twice angle A" which ...
August 24, 2013

project management
It would be an interesting exercise if only we know what it is... we do not happen to have your textbook.
August 23, 2013

precalc
Use the compound interest formula: A=P(1+i)^n A=accumulated amount after n periods (years) P=principal i=interest per compounding period n=number of compounding periods If the smaller investment catches up to the larger one, then the accumulated amounts would be equal. ...
August 23, 2013

math
Hint: substitute u=a^2, then a^4-7a^2+9 =u^2-7u+9 and try to factorize. However, check you question to see if there is a typo. The above expression in u does not have rational factors.
August 23, 2013

physics
Pressure = force / area Force = mg = 2.5*9.81 N a. Area = 10cm * 5 cm =0.10*0.05 m² =0.005 m² Pressure = 2.5*9.81/0.005=4905 Pa Part b can be solved similarly.
August 20, 2013

statistic
This is a binomial distribution with parameters n=3 (number of trials in the experiment) p=1/2 (probability of boys, X) q=1-p (probability of girls) For a random variable X with a binomial distribution (n,p,q), then E(x)=μ=np σ²=npq where σ=standard ...
August 20, 2013

Math
Yes, your next step is to solve for x which represents Oliver's share.
August 19, 2013

MaTh
Correct! Good job! :)
August 19, 2013

Math
yes.
August 19, 2013

French
Just a little elaboration: If "this" stands for a masculin noun, such as a basket (un panier), or a bag (un sac), you could say Y a-t-il des oeufs dans celui-ci? If it stands for a feminine object, such as a pocket (une poche), or a plate (asiette), then we would use...
August 18, 2013

math
If it has 2 AND 3 in the prime factorization, it means that the number must be divisible by 2 AND by 3, which means that it is divisible by 6. The number(s) between 50 and 59 that are divisable by 6 would be 54. The prime factorization of 54 is 54 =6*9 =2*3*3*3 =2133 You can ...
August 15, 2013

MATH
What did you get? You would be well to do the 4x4. If you have difficulties, start with a 1 by 1, then 2 by 2 and then 3 by 3 grid. You will find a pattern that you can use later. Once done, do an n × n grid and check if the answer for n × n works for n=4.
August 15, 2013

math
Mass = mass density * volume where mass density = 23.4 g/cm³ volume = 75 cm³
August 15, 2013

Discrete Mathematics-Elementary graph theory
A cycle graph is like a polygons with vertices along the circumference. A complete graph is one where EACH vertex is connect to EVERY OTHER vertex (except itself). Using these definitions, are you able to answer the question?
August 8, 2013

Discrete Mathematics-Elementary graph theory
No it does not matter. You can even use a wavy line. However, we usually use a straight line unless we would like to avoid certain crossing of lines.
August 8, 2013

Discrete Mathematics
By definition, a tree is a connected acyaclic graph. One of the sufficient properties of a tree is that the number of edges equals the number of vertices minus one. Note: number of edges = (sum of degrees of all vertices)/2.
August 6, 2013

Discrete Mathematics
An Eulerian path is a path which passes through ALL edges exactly once. This can happen if the graph has either 0 or 2 vertices with odd degrees. So even an incomplete graph (with degree 0 at one or more vertices) can have an Eulerian path.
August 6, 2013

Discrete Mathematics
The number of edges =(sum of degrees of all vertices)/2
August 6, 2013

Discrete Mathematics
See your next post to find out how to calculate the number of edges. Hence deduce if such a graph can exist or not.
August 6, 2013

Math- Probablility
C=Casper D=Denver Conditional probability: P(C)=0.4 P(D)=0.3 P(C∪D)=0.27 Probability of having been to Casper given she has gone to Denver =P(C|D)=P(C∪D)/P(D) =0.27/P(0.3) =0.9
July 29, 2013

Probability
5 choose 2 * 15 choose 12 =5C2*15C12 =5!/(2!3!) * 15!/(12!3!) =5*4/2! * 15*14*13/6 =10*455 =4550
July 29, 2013

Calculus-Series
I assume the expression is (n^3)* (e^(-n^4)) for n=1 to +&inf; You can use the ratio test to show that it converges, namely, show that an+1/an < 1 ∀ k≥1. The integral test will result in a definite integral from 1 to +&inf; which is not an elementary function, but...
July 29, 2013

Calc Help Please
Implicit differentiation: (d/dx)(2x^2+2x+xy=2) 4x+2+y+xy'=0 y'(x)=-(4x+2+y(x))/x y'(2)=-(4(2)+2+y(2))/2 =-(10-5)/2 =-5/2
July 28, 2013

Math-probability
8 choose 3 =8C3 =8!/((8-3)!3!) =8*7*6/(1*2*3) =56
July 28, 2013

physics
Take moments about the centre. On father's side: M=70*0.65=45.5 kg-m On children's side: M=(30+30)*x Equate moments and solve for x.
July 28, 2013

Elements of Structures MIT 2.02
Please see: http://www.jiskha.com/display.cgi?id=1374949947
July 27, 2013

Math
3/(3+4)
July 27, 2013

Geometry
We have P1(6,-2), P2(1,3) Use Slope=(y2-y1)/(x2-x1) to find slope.
July 27, 2013

Math- probability
F=fever S=sore throat P(F)=80% P(S|F)=30% But P(S|F)=P(S∩F)/P(F) P(S∩F)=P(S|F)*P(F)=30%*80%=0.24
July 27, 2013

Math (probability)
Conditional probability. P=pool G=garage Probability of a home having a pool given that it has a garage is P(P|G)=P(P∩G)/P(G) =11%/50% =22%
July 27, 2013

Elements of Structures MIT 2.02
Please clarify what are the "other" questions.
July 27, 2013

Elements of Structures MIT 2.02
I have quite different values as you have. It would help if you show your work so we can compare notes. My approach would be: Since the beam is composite, there is only one value of 1/r at each cross section x, which is given by M(x)/EI. For a cantilever beam, M(x) is ...
July 27, 2013

Elements of Structures MIT 2.02
Good luck!
July 27, 2013

Elements of Structures MIT 2.02
1. I suggest you check your EI. 2. You have not confirmed q(x)=q0*x*L (as you have written). I think you mean q(x)=q0*(x/L) If that's the case, I also get δ=-0.0582 as you did. I think the large δ comes from the erroneous EI. If you use EI=8050π, you'd ...
July 27, 2013

Elements of Structures MIT 2.02
Did you use Ix=Iy=πd^4/64 ?
July 27, 2013

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