Friday
September 19, 2014

Posts by MathMate


Total # Posts: 10,735

PHYYYYYSICS 10
Horizontal component of velocity = 18 m/s Vertical component of velocity, Vf, is given by Vf²=Vi²+2*a*Δx Vi=initial vertical velocity=0 m/s a=acceleration due to gravity=-9.8 m/s² Δx=-41 m Vf=sqrt(0+2(-9.8)(-41))=28.4 m/s (downwards) angle with ...
September 18, 2014

physics
Assuming the crate moves upwards. The applied force P is upwards whether the crate moves upwards or downwards at a constant velocity. coeff. of kinetic friction, μ = 0.75 angle of incline, θ = 46° (with horizontal) If crate moves upwards with a constant velocity, ...
September 17, 2014

Mechanism and Machines
It's surprising that your teacher did not mention any application when the subject was being taught. The linkage essentially converts rotational motion into a straight line movement. The rotational motion usually comes from a motor, and the straight line movement can be ...
September 17, 2014

math - fractions
Father does the work in x hours, or father does 1/x of the work in one hour. Son does 1/(2x) of the work in one hour. Together, they do 1/x+1/(2x)=1/6 of the work in one hour. 2/(2x)+1/(2x)=1/6 3/(2x)=1/6 Cross multiply 2x=18, x=9 So father does the wok in 9 hours.
September 16, 2014

Math
Profit = 0 is break even. So solve for x in P(x)=-37x²+1073x-7548 = 0 to give x=12 or x=17 The profit is given by the maximum of the P(x) function, which is located at x=(12+17)/2=15.5, or the maximum profit is P(15.5). (substitute 15.5 for x and evaluate the profit).
September 16, 2014

Math - ratio
Use ratio / cross multiplication 18:162 ≡ 36:x x=162*36/18 = 324
September 16, 2014

math-fractions
Total (in fraction) = 1 Woodwinds = 1-2/5-1/3=(15-6-5)/15=4/15 half of woodwinds (4/15) are clarinets, so clarinets = (4/15)÷2= 2/15 One eighth of brass are tubas, so tubas = (2/5)÷8 = (2/40)=1/20 whole : 240 1/20 : x (number of tubas) x=240*(1/20)÷1 =240/...
September 16, 2014

math-addition
Both Minnie and Amanda have 11 cds, so they have the same number of cds.
September 16, 2014

Physics - kinematics
Given Vi=36 m/s θ=30 Vix=36cos(30)=31.18 m/s Viy=36sin(30)=18 m/s Vy(t)=Viy*t+(1/2)gt² =18*1+(1/2)(-9.8)*1² =13.1 m/s velocity=sqrt(Vix²+Vi(1)²) =sqrt(31.18^2+13.1^2) =33.82 m/s
September 16, 2014

Math - compound interest
i=4% p.a. compounded quarterly = 1% per period Let R=(1+i), n= number of quarters/periods Future value FV=100(1+R+R²+R³....+R^(n-1) ) =100(R^n-1)/(R-1) =100(R^n-1)/i For FV=10000 we have 10000=100(R^n-1)/i R^n=(10000/100)*i-1 =2 n=log(2)/log(1.01)=69.66 It will take ...
September 15, 2014

French
You can also say (formally) "De quel pays êtes-vous venu/venus/venue/venues?" depending on the gender and number of persons to whom you're addressing.
September 15, 2014

trigonometry
Sorry, don't know if you have used Word or other word processors to write the equation, but they do not translate corectly. Here most HTML symbols are recognized, or you could use ^2 to mean square, and sqrt( ) to mean square-root, etc. Also please write the appropriate ...
September 15, 2014

chemistry
Solubility is defined as the number of grams of solute that will saturate 100 grams of solvent at a given temperature. So at 20 degrees, we know that the solubility of CuSO4 is 25. Mass of water (solvent)=80 g Use ratios: 25:100 = x:80 Solve for x to get x=25*80/100=20g
September 15, 2014

Algebra
slope intercept form is in the form y=ax+b If you start from the equation above, you would isolate (solve for) y in terms of x and the constants, then simplify the right-hand side to remove parentheses. Isolate y means use algebraic operations to leave only y on the left-hand ...
September 15, 2014

math
Probability of rolling two even numbers = (1/2)(1/2)=1/4 Expected value of the game, E(x) is the sum of the following: outcome X, probability P(X), X*P(X) 2 evens=+$8, 1/4, +$2 at least one odd=-$2, 3/4, -$3/2 The sum of X*P(X) = $0.50 The expected value is thus $0.50 for each...
September 15, 2014

computer science
Command interpreter is a system where it would execute a command at a time, according to the command the user types in. The turtle graphics window is much the same as a command interpreter, except that the command are simpler (turn, move, etc.) and it displays a graphics ...
September 15, 2014

real analysis
Correction: Somewhere the -8 was inadvertently written as -7, so after corrections, |Xn|≤|-8|+|-1/(n+1)| ∀n∈N or |Xn|≤9 (or M=9)
September 14, 2014

real analysis
Try and improve on the following. R=set of all real numbers. N=set of all natural numbers Let Xn=-8+n/(n+1), where X∈R then Xn=-8 + (n+1)/(n+1) - 1/(n+1) =-7 - 1/(n+1) => |Xn|≤|-7|+|1/(n+1)| (triangle inequality) But |1/(n+1)|≤1 ∀n∈N, therefore |Xn|&...
September 14, 2014

COMPUTER SCIENCE
See response: http://www.jiskha.com/display.cgi?id=1410758490
September 14, 2014

Statistics
A normal distribution is symmetric and unimodol. Therefore an asymmetric bimodal distribution cannot be normal. But beware: A symmetric and unimodal distribution is not necessarily normal. These are necessary but not sufficient conditions.
September 14, 2014

Physics
Acceleration = (final velocity - initial velocity)/ time =(0 - 22 m/s ) / 2 s = -11 m/s² The negative sign indicates that it is a deceleration (slowing down).
September 14, 2014

physics
The police car catches up 2.68 m/s for every elapsed second. So to catch up 25.8 m/s, it will take t=25.8 m/s^2 / 2.68 m/s = 9.63 s Since the speeder travels at a uniform speed of 25.8 m/s, the distance travelled can be calculated by Distance = speed * time.
September 14, 2014

French
The second question is: "Où sont-ils placés par rapport aux noms?" It means where are they ("les mots soulignés", or what you identified in question 1) placed/located relative to the nouns (noms).
September 14, 2014

French
It is a good idea to have the complete context of the question which in this case concerns grammar. I suppose you have learned about the different groups, of which groupe nominal (GN) is one. The (GN) consists mainly of the noun (nom) and determinants. Determinants can belong ...
September 14, 2014

engineering mechanics
Try to doodle a triangle of forces and find that the greatest and least resultants occur when the two forces (x,y) are colinear. When they are additive, we have x+y=17 kN, and when they oppose each other, we have x-y=5 (if x>y). Thus solution of the system of equations ...
September 14, 2014

Physics
Your work is correct, here's the explanation. In a projectile problem, the horizontal (x) motions are independent of the vertical (y) motions. In the case of a horizontally fired projectile from a given height, the problem is equivalent to a free fall from the given height...
September 13, 2014

engineering science
It is not clear if 30 degrees is above or below the incline. The following solution assumes the supporting force is above the incline. You can do a similar calculation if it is below. First, draw a free-body diagram. Resolve all forces along (+ downwards) the incline, and ...
September 13, 2014

math
The usual notation for [x] is the greatest integer that is equal to or less than x. For example, [2.5]=2, [-3.4]=-4, but -[3.4]=-3 because the [ ] function applies to a positive number. The greatest integer not exceeding 3.4 is 3. On the other hand, for [-3.4], the greatest ...
September 8, 2014

statistics
Sorry, I had a miscount. The number of terms of the expansion of (a+b+c+d)^6 is 84 (not 86).
September 5, 2014

statistics
This problem is the same as putting 6 items in 4 bins. Different ways of solving this problem would be: 1. enumerate in a systematic way: 0006 0015 0024 0033 ... 6000 and count how many you've come up with. Note that since the children are of different ages, and the gifts ...
September 5, 2014

Computer Science
Explanation of the pattern follows: ^a specifies the string begins with "a" b\$ specifies that the string ends with "b" d* allows 0 or more embedded d's. (cd+)* requires a "c" to be followed by at least one "d". This can happen 0 or ...
September 4, 2014

Computer Science
Try my $pat="^ad*(cd+)*b\$" Use this pattern to match strings according to the rules specified. Note that $pat will match a qualifying string, but does not define a string. Hope someone else can answer the second part.
September 4, 2014

math
Outer perimeter: 4s=4*10'=40' Spacing = 6" = 0.5'/plant Number required = 40'/0.5'/plant = 80 plants Since the perimeter is a closed figure, there is no need to add one "at the end" as in the case of a linear row with two ends.
September 4, 2014

math urgent please
Don't know if you paraphrased the question, but the question is indeed confusing. First it gave the length of 320 cm and width of 320/2=160 cm. So there is no variable to optimized. Then it talks about maximizing 4 faces, and then jumped to optimizing 3 faces. Finally, it ...
September 3, 2014

calculus - insufficient information
Unfortunately we cannot see fig 2c unless you describe it or send a link.
September 3, 2014

math
Since it is not stated in the question, we assume that the unit of f(x) is in feet. There is inconsistency with the two expressions for f(x), namely f(x)=(1/2)x²+(4/5)x, and later f(x)=(1/12)x²+(4/5)x Solving the first. If the second expression is intended, you can ...
September 3, 2014

physics
Average acceleration =(0-30) m/s ÷ 5 s = -6 m/s² Force = ma = 80 kg * (-6 m/s²) = -480 N (resistive force)
September 3, 2014

math
correct!
September 3, 2014

Physics
Stress = force/area 1. stres= 6.5*10^5 dynes / (π(0.3)²/4 cm²) = 9195619 dynes/cm² = 919.6 kPa Young's modulus nor strain cannot be derived from the given information. 2. Stress = force /area 10 kg * 9.8 m/s² ÷ (π0.004²/4 m²) = 7....
September 3, 2014

Chemistry
Use C1*V1 = C2*V2 For example, to dilute 100 mL of 36M solution to 6M, we put 36M *100 mL = 6M * V2 Solve for V2 = 36M*100mL/6M = 600 mL This means that the 100 mL of 36M solution must be diluted to give a final volume of 600 mL.
September 2, 2014

math
1. -f is the reflection of f about the x-axis. 2. f(-x)=f(x) => f(x) is even 3. f(-x)=-f(x) => f(x) is odd Good job! :)
September 2, 2014

math
Sum of squares = p²+(p+5)² =625 Expand p²+p²+10p+25=625 2p²+10p=600 p²+5p-300=0 (p-15)(p+20)=0 p=15 or p=-20, reject negative root The sides of the squares are therefore: p=15 p+5=15+5=20
September 2, 2014

statistics
A five-number summary represents the following qualifiers: minimum Q1 median Q3 maximum the interval minimum/median represents 50% of the data in the lower half. the interval median/maximum represents 50% of the data in the upper half. the interval Q1/Q3 represents 50% of the ...
September 2, 2014

Precedence rules for the algebra community
Precedence of operators In simple algebra, there is a set of precedence (priority) of operations that should be respected in order that everyone evaluates mathematical expressions in the same way. Although these rules have been taught in elementary school or junior high school...
September 2, 2014

physics
Assuming the mass of the object is negligible compared to the mass of the person and the boat, then the speed of the object is 30km/h in addition to the speed of the boat. Using a terrestrial frame of reference, the apparent speed of the object by a stationary observer on the ...
September 2, 2014

proportions
35' : 0.28 kg x' : 7.2 kg Cross multiply and solve for x x=35' * 7.2 kg / 0.28 kg = 900'
September 2, 2014

college algebra
typo: N = (x+5)*x²/(x+3) =(x³+5x²)/(x+3)
September 2, 2014

college algebra
First, observe the rule of operator precedence, i.e. BEDMAS (brackets,exponents, division/multiplication, addition/subtration) in that order. Q1. I suspect the expression should have been written as (x+5)/(x+3) to be interpreted correctly. Based on that, we know that the new ...
September 2, 2014

mathzzz want answer in simple way
Let x=number of rows, and since number of rows = number of persons per row, we have x*x=3249, or x=sqrt(3249) take out your calculator and find x.
September 2, 2014

math
Sum of angles of a quadrilateral = 360° sum of the other two (C & D) = 360-150=210 If C : D = 2:3, then C+D=210, C: C+D = 2 : 5 = 84 : 210 C=84, D=210-84=126 The first two angles (A & B) add up to 150, which could be A=100, B=50, or A=75, B=75, etc. Without additional ...
September 2, 2014

Math
Correct! Well done! :)
September 2, 2014

isu
mass (m) = density (ρ) * volume (v) = 1.46 g/mL * 59.9 mL = 87.5 g
September 1, 2014

Business Math
Assuming the investment is placed for exactly one year, then the future value is FV=Principal*(1+i) =2989(1+0.03) = $3078.67
September 1, 2014

math
markdown: 12% : $1.20 sale price : 100% : X Cross multiply and get sale price, X = 1.2*100%/12%=$100
September 1, 2014

Math
Probability of getting the first white sock out of 30 socks is 24/30 Probability of getting the second white sock out of the remaining 29 socks is 23/29 Since he needs a pair of white socks, both of the above events (steps) must succeed, for which the probability is the ...
September 1, 2014

physics
Convert values to consistent units: 66 mi/h = 66 mi/h *5280 ft/mi ÷ 3600 s = 96.8 ft/s similarly 55 mi/h = 80.67 ft/s acceleration = -14 ft/s² Time required=(80.67-96.8)/(-14) = 1.15 s Do not forget to add the reaction time, which could exceed the mechanical ...
September 1, 2014

Statics
The angles are not precisely specified. It is not clear whether the a-axis makes an angle of -20 (340) with the x-axis, or -160 (200) with the x-axis. Same problem for the force F. Could you specify forces and axes using the following conventions: 1. All angles are measured ...
September 1, 2014

Statics
So you have three forces, the magnitude and angles of which two are known. You will need to first compile a table of known and unknown values. To avoid confusion, you need to follow these rules for describing forces: 1. All angles are to be measured counter-clockwise from the ...
September 1, 2014

Statics
A description of the accompanying figure is required. Minimally, the directions of F1 and the magnitude of F2 are required.
September 1, 2014

Statics
If Pa and Fb are both 305N, then angles aOF and FOb are equal to 38 ° See http://www.twiddla.com/1746657 Since F*cos(38)=305N, F=305N/cos(38). You can work out the orientation of b from the figure.
September 1, 2014

math
Please proof-read your question. ># is meant for which symbol? To take the limit, x-> ?
September 1, 2014

math
If you divide the second equation by 2 and transpose terms to the same form as the first equation, you will find that the two equations are identical. This is a situation where the two equations represent coincident lines, hence there is an infinitely many solutions.
September 1, 2014

Logic / Discrete Mathematics
You're welcome! :)
September 1, 2014

Logic / Discrete Mathematics
With simple expressions like these, the easiest proof is to make a truth table...unless it is specifically prohibited in the question. Also, there are precedence in the logical operators, just like + - * ÷. see http://en.wikipedia.org/wiki/Logical_connective The ¬ ...
September 1, 2014

science, physics
The heat of fusion of ice is 79.8 cal/deg C. Let T = final temperature, and sum heat change = 0 8 kg (T-20) + 2 kg ((T-0)+(79.8))=0 cal-kg Solve for T to get T=+0.04 deg. C.
September 1, 2014

3D Modling
One of the ways is to download the (free) software, and get familiar with it through tutorials. This way, the question (and many others) will be answered.
August 31, 2014

Business/Finance
June: 30-6=24 July: 31 August:31 September:30 October: 8 Total=24+31+31+30+8=124 days Discount period: The period of time between the date a bill of exchange is drawn and the date on which payment is due. So discount period = 200-124=76 days
August 31, 2014

physics
Kinetic energy, KE = (1/2)mv² resistive force = constant Retaining half the velocity means (1/2)^2=1/4 of the kinetic energy. Since 50% of the KE penetrates 25 cm, so 25% of the (remaining) KE penetrates 12.5 cm.
August 31, 2014

physics
p(t)=3t²-2t+1 W Δp =p(4)-p(2) =41-9 =32 W
August 31, 2014

physics
Power =mgh/Δt / efficiency =100kg*10m/s²*10m/5s / 60% = 2000/0.6 = 3333 W = 3.33 KW Thank you for posting the answers, but there are too many decimal points that I cannot make anything out of them. In addition, (C) and (D) seem identical to me.
August 31, 2014

Physics
585 zag/zoyear =585 *(1/0.18) zig/ (0.4 years) =(585/0.18) zig / (0.4*365*24 hours) = 0.928 zig/hour
August 31, 2014

Engineering
Try http://faculty.uoh.edu.sa/m.touahmia/CE353-CH3.pdf
August 29, 2014

math
The distance between two points with coordinates P1(x1,y1) and P2(x2,y2) is given by the distance formula: D(1,2)=sqrt((x2-x1)²+(y2-y1)²)
August 29, 2014

Math
36 students B:G = 3:1 = 27 : 9 Add x girls, 27/(9+x)=9/5 Solve for x by cross multiplication.
August 29, 2014

algebra 2
|x|-2≤-3 |x|≤-3+2 |x|≤-1 => x≤-1 or -x≤-1 => x≤-1 or x≥1 => on the number line: <------ -1.......0...... 1 ------>
August 27, 2014

Chemistry
The question is not complete. I assume you are asked to find the quantity of CO2 produced by heating 25g of CaCO3. Molecular mass of CaCO3=40+12+48=100 From the equation, 1 mole of CaCO3 produces 1 mole of CO2. Since 25g is 0.25 mole of CaCO3, we conclude that 0.25 mole of CO2...
August 25, 2014

Chemistry
The question is not complete. I assume you are asked to find the quantity of CO2 produced by heating 25g of CaCO3. Molecular mass of CaCO3=40+12+48=100 From the equation, 1 mole of CaCO3 produces 1 mole of CO2. Since 25g is 0.25 mole of CaCO3, we conclude that 0.25 mole of CO2...
August 25, 2014

algebra
* outcome 3 is "hit neither"
August 24, 2014

algebra
Calculate expected gain, E(X), of the venture. If E(X) is positive, it would probably be advantageous to sink a well. Expected value is the following sum: E(x)=Σ G(X)*P(X) where X is a possible outcome, G(X) is the net gain of the outcome, and P(X) is the probability of ...
August 24, 2014

computer science
Looks good to me!
August 24, 2014

algebra
To find the x-intercept, set y=0 and solve for x.
August 21, 2014

maths
You're welcome!
August 21, 2014

maths
Area of each triangular face = (1/2)base*height Surface area of tetrahedron = 4*area of each face.
August 21, 2014

Math
3768 grains mean 3768*1 second=3768 seconds. Convert to hours, minutes and seconds: 3768 seconds / 60 s/min. =62 minutes 48 seconds = 1 hour 2 minutes 48 seconds. The other rewards may be worked out in a similar way.
August 21, 2014

math
4C3(1/2)^3(1/2)^1 =4(1/16) =1/4
August 20, 2014

math
2=2^1 3=3^1 4=2^2 5=5^1 6=2*3 7=7^1 The least common multiple must have factors that satisfy all of the above: 2^2*3*5*7=420
August 20, 2014

math
Mid-point of (3,8) and (9,16) =((3+9)/2, (8+16)/2) =(6,12) Mid-point of (8,11) and (x,13) =((8+x)/2, (11+13)/2) =((8+x)/2, 12) To have the same mid-point, the x- and y-coordinates of the mid points must match. so (8+x)/2 = 6 Solve for x.
August 20, 2014

statistic
Total number of balls = 5+6+6=17 P(RR)=Probability of two reds =(5/17)*(4/16) P(WW)=(6/17)*(5/16) P(BB)=(6/17)*(5/16) Probability of two same coloured balls =P(RR)+P(WW)+P(BB)
August 20, 2014

math
You have assumed compound interest compounded monthly. Assuming these assumptions are correct, then we have total amount F, R=monthly installment deposited at the end of the month, i=monthly interest, n=48, I=1+i, F=R(I^(n-1)+I^(n-2)+...+I^(0)) =R(I^n-1)/(I-1) =500((301/300)^...
August 19, 2014

Basic Algebra
Also, note that factors must exceed 8, from the context of the question.
August 19, 2014

Basic Algebra
See http://www.jiskha.com/display.cgi?id=1408443950
August 19, 2014

Science
You're welcome! :)
August 19, 2014

Science
The independent variable is the amount of money offered, which in this case takes on only two values, $0 and $5. Evidently other experiments could be carried out to have varied incentives, assuming the teacher keeps the job long enough to do further experiments.
August 19, 2014

Applied Programming
Technically you do not need to ask for a 2D or 3D calculation because there is no overlap of the shape names. You will need a string of if-else-elseif-endif statements, or more conveniently a switch statement. Use the "default:" option in case the user feeds a wrong ...
August 19, 2014

chemistry calculations
It is given that the reaction at the given temperature is in equilibrium. Next check if the reaction is homogeneous: all gases, so homogeneous. Now denote the stoichiometric coefficients by a,b and c for the reactants and products respectively (all equal to 1 in this case). ...
August 19, 2014

Basic Algebra
This is more a riddle than math. In my opinion, it is hinged on the word "equally", which could mean equally to the dollar, or to the cent. Taking the first case: everyone has an equal number of dollars. Factoring 5130, we have as prime factors: 2,3³,5,19, which...
August 19, 2014

maths
If we assume that the ordered pairs (x,y) follow a linear rule y=ax+b, we will be able to solve for the rule using two of the ordered pairs, and use the third to check if the rule is appropriate. Thus, for the first ordered pair: y=ax+b => 14=180a+b .... (1) For the second ...
August 17, 2014

MAth
The question as it is has a large number of solutions. In general, optimization problems have an objective function, such as minimum cost, minimum surface area, etc. and subject to constraints, such as maximum number of fruits per box, or maximum sizes, etc. An example ...
August 17, 2014

Precal
Hint: look up triangle inequality. Basically, it says that the sum of the lengths of any two sides of a triangle is greater than or equal to the length of the third side.
August 16, 2014

calculus
The diagonals are obtained by the sum and difference of the two vectors: a+b=<-2,5>+<3,2>=<1,7> a-b=<-2,5>-<3,2>=<-5,3>
August 16, 2014

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