Thursday
September 3, 2015

Posts by MathMate


Total # Posts: 11,307

Math
Use equality of proportions object:shadow x:12 = 5 m : 6 m which means x/12=5/6 Cross multiply: 6x=5*12 Solve for x x=60/6=10 So the tree is 10 m tall
August 26, 2015

BUSINESS CONSULTING
Hmm...It would be nice if you start working on the problem, show some thoughts and work of your own, identify the difficulties, so that we can help you.
August 25, 2015

Math
Hint and example: distributive property means the equivalence of the following expressions: a(b+c) = ab + ac Example: 5(x+4) = 5x + 5(4) = 5x + 20
August 25, 2015

Math
A typical line in slope intercept form is y = mx + b where m is the slope and a is the y-intercept. Two lines are parallel whenever their slopes (m1, m2) are identical. Try to spot two lines with identical slopes and find the corresponding choice of answer.
August 10, 2015

math
Solve for x from the equation: 5x-4 = 2(2x+10) 5x-4 = 4x + 20 5x-4x = 20+4 x=24 so angle ABC = 5(24)-4 = 120-4=116 degrees. What kind of angle is angle ABC?
August 10, 2015

French SraJMcGin
To Rose: If you mean : "if you make up the sentences in English and translate it to French, how to make sure it will be translated to the subjunctive" then SraJMcGin has already given you all the conditions that the sentence should be subjunctive in French. The ...
July 17, 2015

math
Please refrain from starting a new thread when information refers to a previous thread.
June 15, 2015

math
"last one is $300" So you would write a table as follows Date description amount Balance -......bal.brought fwd - 2000 Jan 2...deposit 500 2500 Jan 10..Alex co. 600 1900 Jan. 16 Angels co. 300 --?-- So you can calculate the final balance on the last line.
June 15, 2015

math
It is an optimization problem. Here are some steps to solve the problem: 1. define variables (values that are to be found). 2. Reread the question, and translate each constraint into an inequality. 3. Graph the constraints and select the feasible region, using the variables as...
June 8, 2015

math (incomplete)
There are critical characters that are not legible in the post. Please amend the post, or repost.
June 8, 2015

Math/ASU
For every child ticket, 2.25 adult tickets were sold. This is the same as For every 4 child tickets sold, 9 adult tickets were sold, for a total of 4*2+9*9=$89. Number of sets of sets (4+9) sold = 520/13=40 Total amount = 40*$89=$3560 Alternatively, using algebra, A=number of ...
May 29, 2015

Geometry
surface area = 4πr^2 Volume = 4πr^3/3 S/V ratio = 4πr^2 / (4πr^3/3) = 3/r
May 29, 2015

Math
Base Area = triangle base * triangle height /2 Prism volume = Base Area * height You have been given triangle base: 7 ft triangle height: 4 ft prism height:8.5 ft Apply the above formulas to calculate the volume required.
May 22, 2015

Math- simple polynomials
Can you explain how you got 4 and 1/9 please. I prefer to see you post the answer, not the letters. This way you have an extra chance of checking your answer.
May 21, 2015

Algebra
Hint: Reminds me of the Fibonacci numbers.
May 17, 2015

Math
one light-year is the distance light travels in one year. Light travels at a speed of 3*10^8 m/s. In one year, there are 365*24*60*60 seconds. So one light-year = 3*10^8 * 365*24*60*60 m = 9.461*10^15 m = 9.461*10^12 km (since 1km=1000m)
May 17, 2015

Math
the value is 7 choose 4, or choosing 4 students out of 7 (order does not count). "7 choose 4" can be evaluated as 7C4 = 7!/((7-4)!4!) = 7!/(3!4!) = 5040/(6*24) = 35
May 17, 2015

Calculus 2
hints: use the relations: x=rsinθ y=rcosθ which means the left-hand side =x²+y²=r² Also 8sin2θ = 16 sinθcosθ =16(y/r)(x/r) =16xy/r² Equating both sides, x²+y² = 16xy/r² or (x²+y²)² = 16xy =2xy/(x&...
May 17, 2015

Math (Solving Equations)
No, you do not distribute the absolute value signs. What you did is correct, i.e. keep the absolute value quantity intact, and eventually evaluate the value as either positive or negative. |x-1|=5 means x-1=5 => x=5+1=6 or -(x-1)=5 => x=1-5=-4
May 17, 2015

math
Discount is calculated by the formula: Discount = Maturity value * discount rate * discount period. Here I assume "face value" is what the bearer receives on maturity. So discount = 2200*0.09*140/365 = $75.95 You can read the following link for more details: http://...
May 16, 2015

Computer science
Pseudocode is almost like human language input billed_amount; amount_with_tax=billed_amount * 1.09 Total=amount_with_tax*1.15 output total
May 13, 2015

Math
Exactly, well done! :)
May 12, 2015

Math
In math, knowing the definition of the terms is key to solving the problem. What you have attempted to find is the mean (or average), not the median. Here the key term is "median", defined as follows: "To find the Median, place the numbers you are given in value...
May 12, 2015

Pre-Calculus (absolute values)
Knowing the definition of specific math terms helps solving the problem, most of the time. Here the term is invariant point, which is usually called fixed point, defined as follows (Wiki) "In mathematics, a fixed point (sometimes shortened to fixpoint, also known as an ...
May 12, 2015

Physics
μs determines when skidding will begin. Maximum centripetal force provided by static friction = (μs)mg Maximum speed = v, centrifugal force = mv^2/r At equilibrium, (μs)mg = mv^2/r Solve for v v=sqrt(μs * rg) =sqrt(0.85*215*9.81) =42 m/s approximately
May 12, 2015

To Anono
Lucina has been giving you excellent and patient help. Please appreciate her time dedicated. If you want correct anwers, you need to do your part by checking the questions/answers that you post. Any typo in the post will give you a right answer to the wrong question. For ...
May 12, 2015

Plane Trigonometry
This is a very common problem for surveyors to find distances between two objects which they cannot reach. The same principle is used to find difference in heights. Surveyors can do this today because the newer generation of theodolites can measure distance without a prism ...
May 11, 2015

geometry
factors do not cancel when we add, only when we divide. For example, 2π+5.5π =(2+5.5)π =7.5π or 12πr²+23π =(12r²+23)π
May 11, 2015

math
Assume decimal digits, so there are 9 non-zero decimal digits [1-9]. The probability that the second digit is 8 is one choice (8) out of 9 possible digits = 1/9. Using conditional probability, Let event of getting (8) = 1/9 so assuming independence of the choice of digits, P(...
May 10, 2015

math
Use amount = principal * ert where principal = initial investment e=napier's constant=2.7182818284... r=annual rate of interest t=time in number of years Example: 1000$ invested for 3 years at 6% amount = 1000 * e0.06*3 = $1197.22
May 10, 2015

Maths
Fast method: Ratio of boys to girls = (69-65):(75-69) =4:6 =2:3 Number of boys = 80*2/(2+3) = 32 Standard method: Let x=number of boys (75*x + 65*(80-x))/80 = 69 Solve for x 75x-65x = 69*80-5200 = 320 10x=320 x=32 Answer: there are 32 boys.
May 10, 2015

algebra
Use Amount = principal * (1+i)^n principal=initial investment number of periods (of 3 months) = 10*4=40 i=interest per period = 3.5%/4=0.00875
May 10, 2015

Linear Functions
As an example, e=300 means she earns 300 per week flat salary. e=0.05s means she gets paid 5% of weekly sales. If she gets both a base salary and a commission of 5%, then e=300+0.05s Adapt the example to solve the given problem.
May 9, 2015

math
As a rough approximation, we will assume that the decrease in area is directly proportional to time. 1. Calculate the number of months between September and March = 6 2. Calculate the total decrease in area = (18-3) = 15 million square kilometers. 3. Calculate average decrease...
May 9, 2015

Math
In math, knowing the definition of related terms can help solve a large number of problems. For example, if we know the definition of price elasticity, we can solve the above problem. Definition: The elasticity is represented in numerical form, and is defined as the percentage...
May 7, 2015

Math
Start with the anti-symmetry of sine sin(x)=-sin(-x) so sin(-15°)=-sin(15°) Now use cos²(x)-sin²(x)=cos(2x) cos²(x)+sin²(x)=1 Subtract first equation from second: 2sin²(x)=(1-cos(2x)) sin(x)=sqrt((1-cos(2x))/2) Put x=-15° sin(15°) =-sin...
May 6, 2015

university of hartford
If velocity = v(t), then displacement s(t) = ∫v(t) Use s(0)=6 to determine the constant of integration. For example, if v(t)=3x² then s(t)=∫v(t)=x³+C Given s(1)=4, we have 1³+C=4 => C=3 So s(t)=x³+3
May 6, 2015

probability
1. correct For the rest, think about: 2 & 3 Probability of two independent events: for two independent events A and B to both happen, the probability is P(A)*P(B) Example: The probability of throwing a 4 from a number cube AND drawing a red card from a standard deck is (1/6)*(...
May 5, 2015

Math
sx=reflection about the x-axis (x,y)->(x,-y) so (x, 2(x+3)^2-1 ) -> (x, -(2(x+3)^2-1)) = (x, -2(x+3)^2+1) Now apply the translation of 5 units down to get the answer.
May 5, 2015

mathematic
base radius = r = 5 cm cone height = h = 12 cm Use Pythagoras theorem to find slant height slant height, L = sqrt(5²+12²) =sqrt(169)=13 cm Total surface area = π r²+πrL Substitute numerical values to get numerical answer.
May 5, 2015

Calculus
When f'(x) > 0, the function is increasing. Conversely, f'(x) <0, function is decreasing. Thus the function is increasing in the interval (-∞,-3], and decreasing on [-3,∞). This makes a maximum at x=-3. Since we do not know anything about f"(x), ...
May 4, 2015

Math-Probability
Could you please post the whole question in its original form before you make your comments, please? What is not clear is if the audit is selected/done only on those who got a refund, or a selected proportion (1.01%) of all the returns are selected at random for audit. ...
May 3, 2015

Math-Conditional Probability
Please post the exact original text of the question. We need to examine the wording, even the punctuation to interpret correctly the given information. Confirmation is needed for: - is 85.6% out of the unaudited general population? - Are 49097 and 1342674 the revised ...
May 3, 2015

Trigonometry
Very true, thanks Steve.
May 3, 2015

Trigonometry
Many math problems can be solved by understanding the definition of the key term involved. In this case, the key term is the inverse of a (trigonometric) function. From Wikipedia: "In mathematics, an inverse function is a function that "reverses" another ...
May 3, 2015

Math
When adding polynomials, group like terms (which have identical powers of variables). (8x^2 + x^2) + (- 7x - x + 2x) + (5y - 3y) notice how the x terms were grouped, preserving all the signs. The first group (8x²+x²) would give 9x² with no ambiguity. The same is...
May 3, 2015

statistics
In a normally distributed random variable, the probability of X≤μ is exactly 0.5, since the normal distribution curve is symmetrical.
May 2, 2015

Math HELP! Ms.Sue
First you need to be able to interpret the stems and leaf plot (since there are two stems). The two bars enclose the 10's digit, and the numbers to the left of the first bar represent the units digit for soil A, and the numbers to the right of the second bar stands for the...
May 2, 2015

math
The answer is correct. Don't know what you did until you posted your work.
May 2, 2015

Physics Help Please --- Telescope
b. Magnification is a pure number (no units) c. When turned around, fe=17, fo=114 M=?
May 2, 2015

Maths(URGENT ANSWER please )
The series 1 + 4/3! + 6/4! + 8/5! is Σ2k/(k+1)! for k=1,∞ =2Σk/(k+1)! k=1,∞ =2Σ(k-1)/k! k=2,∞ =2Σk/k!-1/k! k=2,∞ =2Σ1/(k-1)! k=2,∞ - 2Σ1/k! k=2,∞ =2Σ1/k! k=1,∞ - 2(Σ1/k!-2) k=0,∞ =2...
May 2, 2015

engineering mechanics
We don't get to know because we do not have the chance of looking at the numerical values in the diagram that you have in front of you.
May 2, 2015

algebra
If √N=a√3 then N=a²*3 = 3a² Substitute 3 integer values of a to find 3 possible values of N.
May 1, 2015

conditional probability
Many basic math problems can be solved by understanding the definition of terms. Conditional probability P(E|F)=conditional probability that event E will occur given that event F has already occurred = P(E∩F)/P(F) Therefore P(F|E)=P(F∩E)/P(E) =P(E∩F)/P(E) since the...
April 30, 2015

probability
First make a 6x8 table of the possible outcomes (sample space, 48 points). For random throws, each of the 48 points has equal probability (p(i,j)=1/48). a. Expected value of sum of two dice: E[X]=Σ p(i,j)(i+j) i=1,8, j=1,6 Where p(i,j)=1/48, and i+j can be taken from the...
April 30, 2015

maths
Knowing that one mango costs $2.40, we can set it up as 2A+2(2.40)=5A+2.40 and solve for A.
April 28, 2015

Math 222
A perfect square has the form (y+a)²=y²+2ay+a² If you compare with y²-18y+a² you can find a by equating the second term and solving for a: 2ay=-18y
April 27, 2015

Chemistry
* molar mass
April 27, 2015

Chemistry
The N:O ratio can be obtained by dividing the % mass by the respective atomic masses, namely N:O = 30.4/14 : 69.6/16 = 2.17:4.35=1:2 Use the 5.25g sample and the ideal gas law to find the molecular mass and hence the composition.
April 27, 2015

Chemistry
Convert the volume to V at 1 atm. At 25°C, the molar volume is 24.465 L. Use proportion to find the molar mass, M 0.642/V = M/24.465
April 27, 2015

statistics
The sample space has 36 equiprobable outcomes. You can enumerate the successful outcomes and divide by 36. Here's another approach: Success of at least one odd number means that a failure is when both are even. Probability of a failure is (1/2)*(1/2)=1/4, we gather that ...
April 26, 2015

Physics
From the given information, we deduce that It takes 4.184 J/g * 1000 g = 4184 J to raise the temperature of 1 L of water by 1°C. Assuming that all 1000J of heat are absorbed by the 1 L of water, then by proportion, the temperature increase equals 0.239°C. 1°C * (...
April 26, 2015

STATISTICS
See earlier Q & A.
April 25, 2015

statistics
Yes, you can find the answers if the distribution curve is known. The standard normal distribution curve has an area of 1.0 under the curve. To convert a curve with mean 100 and SD=15 to the normal curve, we use Z(X)=(X-μ)/σ which means X=σZ(X)+μ where &sigma...
April 25, 2015

Math
I agree.
April 25, 2015

PHYSICS answer check
Please show equations or calculations used in obtaining your answer so that we can help you check your work.
April 25, 2015

DISCRETE MATH
The finite population has 100 devices, out of which 80 are non-defective. At each draw, both the total number devices and the number of non-defective device decrease, we have the running probabilities as: {80/100, 79/99, 78/98, 77/97, 76/96} the product of which give 0.31931, ...
April 24, 2015

numerical methods
Correction: V(h) should read: V(h)=π(3h²R-h³)/3 =πh²(R-h/3)
April 23, 2015

numerical methods
When the tank has 6.3 ft of oil, the dipstick will be wet by 6.3 feet if it is inserted vertically to the very bottom of the tank. The radius of the surface of water at height x in a sphere of radius R is given by r(x)=sqrt(R^2-(x-R)^2) By integrating r(x) with from 0 to ...
April 23, 2015

chemistry
molar mass of CH3COOH =(12+3+12+16+16+1) =60 mass of acetic acid in 250 mL of 0.26M =(250/1000) L * 0.26*60 = 3.9 g
April 15, 2015

More math
9C4=9!/((9-4)!4!) Use your calculator to work that out.
April 15, 2015

Math
nPr=n!/(n-r)! 6P2 =6!/((6-2)!) =?
April 15, 2015

Simple math.
n! = n(n-1)(n-2)...(3)(2)(1) for example, 3! = 3*2*1=6 You can use the ! or factorial function of your calculator to find the answer for 5!. You can also calculate the products long-hand.
April 15, 2015

maths
clarification: Hint: DC is not parallel to AB unless ∠DAB is 90°.
April 15, 2015

maths
It is an excellent exercise to follow instructions in order to draw a diagram. I would let you do just that, and at any step the statement is incorrect, it is the required answer. Hint: DC is not parallel to AB.
April 15, 2015

physics - good catch!
Haha! At least someone noticed that! Yes, in my days, slide-rules were not accurate enough, and survey calculations were done using 7-figure (log and trig) tables which were packed in a volume (I still have one!) thicker than today's calculus textbook. That taught me how ...
April 15, 2015

basic trigonometry
I hope you mean the ski track along the mountain is 235 m long. The mountain can be represented by a right triangle with the two legs horizontal and vertical, and where the angle of elevation is 35°. The ski track is the hypotenuse (C), and if the horizontal leg (B) and ...
April 15, 2015

math-need figure
To ollie: The question is meaningless without the accompanying diagram. You could post a link to the diagram, or you can describe what the diagram looks like. Sorry that we cannot go further without the rest of the required information.
April 15, 2015

linear algebra
Use the properties of linear transformations: 1. T(A+B)=T(A)+T(B) 2. T(kA)=kT(A) then let A=[1,1], B=[-1,1] and T(A+B)=T(0,2)=[-2,1]+[3,2]=[1,3] => T(0,1)=[1/2, 3/2]=P and T(A-B)=T(2,0)=[-2,1]-[3,2]=[-5,-1] => T(1,0)=[-5/2, -1/2]=Q So (a) L(-1,5)=-P+5Q =-[1/2,3/2]+5[-5/2...
April 15, 2015

statistics
7 choose 5 = 7C5 = 7!/((7-5)!5!) = ? ! means factorial.
April 15, 2015

statistics
probability is constant and independent of trials. trials are Bernouli, i.e. either success or failure. Number of trials is known. All this point to the binomial distribution where P(k successes out of n) =nCk p^k (1-p)^(n-k) p=probability of success of each independent trial=...
April 15, 2015

physics
Solve for n in PV=nRT 2.79*10^5(3.66)=n×8.314462175×(19.8+273.15) to get 419 moles (3 sig. figures) and similarly solve for P in P(7.20)=419.235(8.314462175)(28.5+273.15) to get 1.46*10^5 (3 sig. figures) Your approach is correct, but cannot tell where you got ...
April 14, 2015

physics
131 m. :)
April 14, 2015

Mechanical Principles
corrections. I forgot to multiply F(x) by x in the integral. So T should read less than 6 kN instead of 10.
April 13, 2015

Mechanical Principles
We have an increasing hydrostatic pressure varing from zero at water surface to the depth of the water, which exerts a varying force on the gate. The tension on the cable can be obtained by taking moments about the hinge of the gate (at the bottom). Let H=height of gate (where...
April 13, 2015

CIRCUITS
Resistance across resistors in series = R1+R2+R3 Voltage across each resistor is proportional to the fraction of each over the total. For example, resistors R1=2,R2=1,R3=3, ohms are connected in series and subject to a voltage of 12 volts, Resistance of resistors in series R=...
April 12, 2015

Math
For a rectangle, area = length × width perimeter = 2(length + width). Example: for a rectangle with length = 5 ft width = 3 ft area = 5×3 = 15 square feet perimeter = 2(5+3) = 16 feet
April 12, 2015

maths
Volume of a cube, Vc = (side length)³ Volume of a cylinder Vcy= πr²*h where h=length/height of cylinder r = radius of base = diameter of base /2 If their volumes are equal, then Vcy = Vc πr²*h = side³ Solve for h.
April 11, 2015

geometry
Height / distance = tangent so distance = height / tangent = 28 ft / tan(11°) = ...
April 10, 2015

maths
SI=simple interest formula is Interest = Principal * annual interest rate * number of years = 225 * 0.16 * 3.75 = 135 Add interest to principal to get final repayment amount.
April 10, 2015

Combinations-Math
74 is correct.
April 10, 2015

physics. urgent answer please
F1=10 N at 60° F2=15 N at 0° Use x- and y-components method: x-component Fx=F1*cos(60)+F2*cos(0) =20 N y-component Fy=F1*sin(60)+F2*sin(0) =8.660254 N Resultant, R= √(Fx²+Fy²) angle, θ = atan2(Fy, Fx) Hints for checking your answer: 20 N < R &...
April 10, 2015

French
The words are in the right places and the right form, except for #2 where the number does not agree with the definite article "le". It should be either l'assiette (sing., more probable) or les assiettes (plur.) Not knowing the instructions nor the purpose of the ...
April 9, 2015

linear algebra urgent
http://www.jiskha.com/display.cgi?id=1428173198 Also, remember that u3=u3-p(u1,w3)-p(u2,w3) where p(u1,w3) is the projection of w3 on u1, etc.
April 9, 2015

linear algebra urgent
see other post
April 9, 2015

Math
Assuming that strawberry on vanilla is considered the same flavour as vanilla on strawberry, i.e. order of the two scoops doesn't count, then there are 30C2 possible flavours, and 3 cones for a total of n=3(30C2) possible ice creams. For an order of 12 different ice-creams...
April 9, 2015

math
If you could post the question exactly as you were given, it would be possible for us to understand what you need. Especially in math, paraphrasing tends to lose important information.
April 9, 2015

maths
If the GP has its third term as 9 times its first term, then the sequence is a, ar, ar² where a is the first term, ar is the second term, etc. This means that ar²/a = r²=9, or r=3. Similarly, the fifth term divided by the second term should be a^4/a^1 = a^3, or ...
April 9, 2015

Math
The quadratic formula assume the equation to be: ax²+bx+c=0 (i.e. all terms are on the left-side of the equation). Rearrange the equation to be 3x²+4x-6=0 and try again. You do not need a graphing calculator to find the zeroes. Either by hand, or a regular calculator...
April 9, 2015

Trigonometry (identities) (last help needed)
Typically with simplification like these, you would convert all functions into sine and cosine, and simplify from there on. Use sin²x+cos²x=1 whenever appropriate.
April 9, 2015

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