Sunday

August 30, 2015
Total # Posts: 11,307

**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*

**Geometry**

A plot of the three lines L1, L2 and L3 may be viewed here: https://imagizer.imageshack.us/v2/500x300q90/674/pUzIJX.png
*August 16, 2014*

**Geometry**

This problem is very interesting, and as Steve pointed out, there are 4 circles each of which is tangent to all three lines. This prompted me to look for a general solution for all four circles. If we first examine the condition of tangency of a circle C: (x-a)²+(y-b)&...
*August 16, 2014*

**math**

You're welcome! :)
*August 15, 2014*

**math**

When the perimeter of the triangle is doubled, it is 24. The perimeter before it is doubled is therefore half of 24=12. An equilateral triangle is a triangle with three equal sides. Perimeter = 12 Number of sides of an equilateral triangle = 3 Can you find the length of each ...
*August 15, 2014*

**loyla**

There is a black and a white ball left in the bag after pulling out the first. Can you find the probability of pulling out a black ball from a bag containing one black and one white ball?
*August 15, 2014*

**physics**

Use ratios, 15 g : 0.1 L 75 g : x L solve for x by cross multiplication.
*August 15, 2014*

**physics**

Let maximum velocity be x then x/α+x/β=t Solving, x=t/(1/α+1/β) =αβt/(α+β)
*August 15, 2014*

**riddle?**

Is this a question or a riddle?
*August 15, 2014*

**Math: Equivalence Classes**

To explain in more detail, we would investigate the relation: (a-2d)=(c-2b) Transposing terms, we get the same relation as (a+2b)=(c+2d) Hence all elements (a,b) in the equivalence class would have the same sum a+2b. For example, if the sum is 10, we can have 4 elements: (2,4...
*August 14, 2014*

**Math: Equivalence Classes**

If you haven't read the following link, you can read it before reading on: http://www.jiskha.com/display.cgi?id=1407879480 The idea of solving parts (a) and (b) of the linked question is to establish a methodical way to solve (c) and (d). The typical approach to solving ...
*August 14, 2014*

**math**

Area of a square = (length of each side)² If each side is measured in inches, the area is in square inches, or in².
*August 13, 2014*

**statistics**

Start with a table: R=rain (20%), ~R=no rain (80%) W=windy (30%), ~W=not windy (70%) If rain and wind are independent, the combined occurrence is the product of the respective probabilities. Example: (a)P(R∧W)=.2*.3=0.06 (b)P(~R∧~W=0.8*0.7=0.56 (c)... Will leave (c) ...
*August 13, 2014*

**statistics**

Total number of males =25+10+8=43 Total number of clients = 100 Selection is random. => Probability, P(M) = 43/100 = 0.43 You can proceed with the remaining questions in the same manner.
*August 13, 2014*

**Math**

As Reiny pointed out, the rings and chirps will occur at the same time every 6 seconds, or at 6, 12, 18, 24, 30, 36,.... seconds. So which of the 4 choices will be a moment where the two sounds will occur together?
*August 13, 2014*

**math**

Draw a diagram on paper according to the given information, and the answer will be on paper.
*August 13, 2014*

**math**

You don't have to solve each one, and you don't even need a calculator if you understand the following rules for integer calculations: Multiply: only odd*odd will give odd power: only odd to any power will give odd Add/subtract: only odd±even will give odd. Note...
*August 13, 2014*

**phy**

The few problems you have posted at the same time indicates that you are in the process of learning how to draw a free-body diagram (fbd). Follow your instructor's directions to draw a fbd and identify the triangle to be solved. You should end up with a right triangle in ...
*August 13, 2014*

**Chemistry**

Ammonia is NH3. The mass composition is the ratio of atomic masses (AM) within the molecule, i.e. mass composition of nitrogen =AM(N)/(AM(N)+3AM(H)) =14.0067/(14.0067+3*1.0079) =0.822 approximately.
*August 13, 2014*

**ias question**

If the question were "how do we write 13 aug 2014 in 5 letters without using numbers." then see http://www.jiskha.com/display.cgi?id=1400681438
*August 13, 2014*

**math**

The factor theorem helps us to say that the possible integral roots are in the form of (x±k), where k is a possible factor of the constant term (12) divided by a possible factor of the leading coefficient (1). Thus for the given problem, the possible integral zeroes are &pm...
*August 13, 2014*

**Math**

Hints: It can be shown by calculus that the maximum area of a polygon enclosed by a fixed length of perimeter is a regular polygon, i.e. a polygon with all sides and interior angles equal. It follows from the above that the maximum area enclosed by a fixed perimeter is a ...
*August 13, 2014*

**Physics**

1 HP = 745.6999 W 4 HP = 2982.7996 W 4t = 4000 kg Use mgh=PΔt h=PΔt/mg =2982.7996*10/(4000*10) =0.75m approximately
*August 13, 2014*

**maths**

Correct! Well done! :)
*August 13, 2014*

**maths**

use proportions/ratios: 1 7/8 : 2 1/2 ≡ x : 4 Simplify ratios: 15/8 : 5/2 ≡ x : 4 15 : 20 ≡ x : 4 3 : 4 ≡ x : 4 Solve for x.
*August 13, 2014*

**math**

Use ratio/proportions: 5.58 : 318.76 ≡ x% : 100 Product of means = product of extremes 318.76*x% = 5.58*100 x% = 5.58*100/318.76 = 1.75% approx.
*August 13, 2014*

**fractions/math / Help!**

With what Reiny showed, there should be sufficient information to work out 425 by yourself as an exercise. I will give you another example, 525: 525÷5=105 105÷5=21 21÷3=7 since 7 is a prime we cannot go further. so 525=5*5*3*7=3*5²*7 You're ...
*August 12, 2014*

**collge sydney**

Hints: Kinetic energy of a rotating object is given by: KE = Iω² I is moment of inertia in kg-m² and ω is angular velocity in rad/s. 1 RPM= 2πradians/60 s = π/30 rad/s.
*August 12, 2014*

**Algebra**

Correct! Well done! :)
*August 12, 2014*