# Posts by MathMate

Total # Posts: 12,103

Chemistry
I don't know if you researched for answers, or if you researched for data. Whenever there are two cations and a single (or multiple) anions are in the same aqueous solution, we should first check if any of the combinations of cations and anions might be insoluble and hence...

Calculus
Use the product rule, d(sin(x)cos(x))/dx =cos(x)dsin(x)/dx+sin(x)dcos(x)/dx =cos²(x)-sin²(x) Next use sin²(x)+cos²(x)=1 to transform the above result to one of the provided answers. Note: an easier way to derive the given expression is to make use of the ...

algebra
What was posted does not represent an equation. Please check before posting. If I assume the second / is an equal sign, then the equation reads: (v^2 + 6v+8)/(v^2 + v - 12) = (v+2)/(2v-6) To solve this equation, we start by factoring the quadratic expression into: (v²+6v+...

Algebra 2 (to Jazzy)
Good, then you know what to change.

Math
Let the longest piece be 9x. Then we equate total length 294=2x+3x+9x=14x solve for x and hence calculate the longest piece equal to 9x.

Physical Science
It's normal that your book does not have the answers. However, it's time to review the topics "refraction" and "diffraction" with the help of your book.

Mathematics

physics
The following link explains the solution to a similar problem and helps you get familiar with the standard formulas used in kinematics. http://www.jiskha.com/display.cgi?id=1426656652

Science
Here's an article that explains how MRSA's resistance to antibiotics has evolved, touching on horizontal and vertical evolution. http://evolution.berkeley.edu/evolibrary/news/080401_mrsa

physics
See answer to a similar problem: http://www.jiskha.com/display.cgi?id=1383603887

physics
See solution to a similar problem: http://www.jiskha.com/display.cgi?id=1321918140

Calculus
Use the power rule: https://www.mathsisfun.com/calculus/derivatives-rules.html

Math
f(x)=x^sup2;-5 Use the power rule to find f'(x) => f'(x)=2x at point P(2,-1), x=2 therefore f'(x)=f'(2)=2*2=4 Slope of the tangent equals the derivative of the function at the point in question.

Physics
If it means to boil dry the water in the tank, then it takes 540x calories to boil it dry, compared with 80x to raise the water to 100°C. However, question says: "will make the water boil and keep it at that state" and does not say the tank must be boiled dry!

Physics
The first option: 1 calorie raises the temperature of one gram of water by 1°C. So 80 cal raises the temperature of 1 g of water by 80 degrees. (80°=100°-20°) So it takes 80x cal.to raise the temperature of water to the boiling, where x is the mass of water in ...

physics
Use ΣmCΔT=0 Let m1=mass of ice required. m2=mass of water to be cooled = 200 g T11=-14 T12=10 T21=25 T22=10 Specific heat of water = 1 cal/g/°C Lf=latent heat of fusion of ice = 80 cal/g Heat lost by water: mCΔT =200*1*(25-10) =3000 cal. Heat gained by ...

Physics
Absolute pressure is the pressure on a surface including atmospheric pressure. Gauge pressure is the additional pressure acting on a surface over and above atmospheric pressure. At the ocean depth of 1000 m, gauge pressure is the pressure exerted by the weight of water above ...

physics
Let s=specific gravity of mercury=13.6 K=point at lower end of water column h=height of mercury above K in the other column then equate pressure at K on both arms: 13.6*1.00 = h*13.6 solving, h=1.00 cm This means that the mercury level was at 1.00/2=0.50 above K before adding ...

physics (to Cameron/Tyler)
Among the 9 physics questions you have posted within the last 24 hours, you have not shown any effort on your part. Is it because you have absolutely no idea about the subject, or is it because you'd like someone else to do the work for you? If it is the former, I suggest ...

physics
Assuming no loss in the impact(s), then, let M=mass of Juggles and equate gravitational potential energy (g=acceleration due to gravity) 75kg*g*2.5=M*3.7*g Solve for M.

If we apply linear approximation using calculus, then: V=πr^2h dV/dr=2πrh ΔV≈2πrhΔr =2π(4)(12)(+0.2-(-0.2)) =2π(4)(12)(0.4) =38.4π

Physics
Newton is kg-m/s² Since both sides of the equal sign must have the same units, we conclude: a * m = kg-m/s² and B *kg/m = kg-m/s² Find the units of a and B by solving the two given equations.

Physics
Ignoring dissipative losses (air resistance, friction, etc.), difference of kinetic energy equals work done, => (1/2)m(28.3^2-23.3^2)=226000 j Solve for m.

Maths
There is at least one great circle that passes through any two non-coincident points lying on a sphere. If the two points are diametrically located, there is an infinite number of great circles that pass through the two points. The proof is relatively simple. The two points ...

Maths
Assuming the earth is a perfect sphere, and with a radius of 6400 km, there are exactly two parallels with a radius of 2500 km, located at approximately cos-1(2500/6400) =67° N or S.

Maths
See response to related/similar problem. http://www.jiskha.com/display.cgi?id=1454498132

math
The reflex angle of a given angle is the larger between the angle itself, and the angle formed by 360 minus the angle. For example, the reflex angle of 150° is 360-150=210°. Since angle pqr=1 1/2 right angles = 135°. Calculate the reflex angle of 135° by ...

math
We started with k tags. after students, we have k-k/2=k/2 left. after parents, we have k/2-100 left after teachers, we have (k/2-100)(1-3/5) left You can simplify the last expression to present the final answer.

Statistics
Use Z=(X-μ)/σ where Z=z-score X=variable value μ=mean σ=standard deviation Assuming normal distribution, the left-tail normal distribution table gives the probability of the z-score (or less). Example, part (a): If N=300 and random sampling, we can assume ...

Math
Draw a Venn diagram with three overlapping circles A, B and C. Hint: start with the area A∩B∩C (in the middle) and work outwards. When completed, it will be a snap to answer the given questions.

math
(a) N = 11 choose 2 (=11C2) (c) 11 choose 2 less 7 choose 2, i.e. N minus number of ways of choosing two men.

Math
If there are 14 people, there are 14C2 ways to choose the 2 alternatives. If there are 15 people, there are 15C14 ways to choose the 14 people. So the number of ways of choosing 12 jurors and 2 alternatives is 15C14*14C2

Math
We know that time=distance / speed In this case, time = total distance / total speed =1029 miles / (45+53) mph = ? hours

Chemistry
Use the ratio of atomic mass to the molecular mass. For example, to find the number of grams of Na in 20 g of NaOH atomic mass of Na = 23 molecular mass of NaOH=23+16+1=40 mass of Na in 20 g of NaOH =20g*(23/40)=11.5g

EmberShy
Yes, because (-6.8)² =(-1)²(6.8)² =(1)(46.24) =46.24 Be aware of usage of parentheses, for example: (-2)² =(-1²)(2²) =(1)(4) =4 BUT -2² =-(2²) =-(4) =-4

Math 12
The standard equation for depreciation is FV=PV(1-i)n where FV=future value PV=present value i=depreciation rate per annum, in decimals n=number of years Example: Find the value of a car after 10 years if it was purchased for 50000 and depreciated at 20% per year. PV=50000 i=0...

Geology and soils
Void ratio, e, is the volume of voids, Vv, divided by the soil volume Vs. Total mass, M=37.82-16.15=21.67 Mass of solids, Ms=34.68-16.15=18.53 Gs=S.G. of soil particles = 2.7 => Vol of soil, Vs=Ms/Gs=18.53/2.7=6.863 mL air-void content, ac=0 => all voids are filled with ...

Chemistry
The first three questions may be solved using the relation: molarity (mols) = number of moles / volume (L) where number of moles = mass (g) / molar mass (g). Example: 10.0 g of NaCl is dissolved to make 0.523 L of solution. Find molarity of the NaCl solution. number of moles...

math
Regular price = 4 shirts at sale price 2*regular price = how many shirts at sale price ?

Science, Chemistry
First write the neutralization equation: NaOH+HNO3 -> NaNO3+H2O so C1V1=C2V2 2.0M*0.25L=XM*1.050L Solve for X and compare with 0.48. Pay careful attention to significant figures.

Physics
Convert initial velocities to m/s 60 km/h=60*1000/3600 m/s=16.67 m/s 180 km/h = 50 m/s Use kinematic equation: v^2-u^2=2aS where u=initial velocity v=final velocity a=acceleration (deceleration is negative) S=distance travelled before stopping

algebra
The minimum of a parabola is the y-value of the vertex. See previous response.

algebra
By completing the square, y=x^2-4x-32 =(x-2)²-4-32 =(x-2)²-36 The line x-2=0 passes through the vertex, hence the vertex is (2,y(2))=(2, -36) The line of symmetry of a parabola that opens up or down is the vertical line through the vertex.

algebra
When the leading coefficient is positive, a parabola opens up. Leading coefficient is the coefficient of the term with the highest degree.

math
Answer is good up to (0.4k+0.6w) L. Since we do not know the values of k nor w, their coefficients cannot be added together. The correct answer would be (0.4k+0.6w) L.

math
Example to help you: 30% of 4L of orange juice is added to 70% of 5L of grapefruit juice, find the total volume. Volume of orange juice = 30% of 4L =0.30*4 =1.2L Volume of grapefruit juice=70% of 5L =0.7*5 =3.5L Total volume = 1.2L+3.5L=4.7L

Physics
(a) Law of conservation of momentum: m1v1+m2v2=(m1+m2)v since m2=0.1m1 m1v1+0.1m1v2=(1.1m1)v solve for v v=(m1)(v1+0.1v2)/(1.1m1) =(v1+0.1v2)/1.1 (b) Assuming no loss in total energy, and assuming v1>v2, then the shark itself (without food) has lost energy, since its ...

kelvin
In geometry, drawing a sketch from given information is half-way to the solution. Note bearing is measured clockwise from North. If you draw the sketch in Cartesian coordinates, using P at the origin, you will have P(0,0) Bearing 150°? ?=90-150=-60° in Cartesian ...

Geometry
You're welcome! :)

Geometry
By the law of segments, mCB+mBD=mCD so 4w-4 + 2w-8 = 24 Solve for w.

Math
Yes, your approach is correct, except watch for the following. (1) In principle, part (A) should be done using calculus. If you have not done calculus before, what you did is appropriate, EXCEPT that the interval for p between 4 and 2 is way too large because q(p) varies ...

chemisry
Solubility is the amount of solid that dissolves in 100g of water at the given temperature. 10.1 g dissolves in 50 g H2O at 25°C X g dissolves in 100 g H2O at 25°C Solve for X.

chemistry
Cu(II) oxide is CuO so 3CuO+2NH3 → 3Cu+N2+3H2O From 2NH3 and 3CuO, we conclude that 2 moles of NH3 reacts with 3 moles of CuO to form 1 mol of N2. Find the molar masses of NH3 and CuO and determine which is the limiting reagent. Use stoichiometric ratios to ...

physics
Kinematics equation with zero initial velocity: h=(1/2)gt^2 => time, t = √(2h/g) seconds h=49', g=32.2 ft/s² speed = distance/time = (80-3)/t ft/s =44.14 fps

Algebra (math)
horizontal lines have zero slope, so rate of change (=slope)=0. Any straight-line function has the form y=mx+b where m is the slope, and b is a constant. Compare this with the equation of function 2 to determine the slope. Since rate of change of function 1 is zero, so ...

maths
smallest number with 3 different digits: 100000...000002 assuming leading zeroes do not count. Add enough zeroes in the middle to satisfy the minimum number of digits. Example: 1,002 in the thousands 1,000,002 in the millions, etc.

Math
It depends on how many tests you have had, and what you will get for the final.

Math
Distribute and simplify: (1/3)x(15x-12y)-(1/2)(6x-4y) =x(5x-4y\)-(3x-2y) =5x²-4xy -3x +2y

Maths
A rhombus has four equal sides. One way is to prove that the two triangles on each side of a diagonal are congruent. Since the altitudes of these isosceles triangles are congruent and are the altitudes of the rhombus, the altitudes of a rhombus are congruent.

chemistry

chemistry
Answer is in the products of the reaction. The reactants are already known. H2S (g) +Zn(NO3)2 (aq) &rarrow; ZnS (s) + 2HNO3 (aq)

maths
Each free cube has a surface area of 6(10²)=600 cm² exposed. Each cube with one face connected has 5(10²)=500 cm² exposed. Each cube with two faces connected has 4(10²)=400 cm² exposed. If n cubes are joined together, there are 2 (end) cubes with ...

math
Sorry, I don't understand what your "working" is trying to do, but in any case, 8+5≠13/2≠11.5 and so on, so some corrections on your part need to be done. Given that a:b = 8:5 and b:c= 3:4 What we need to do is to multiply each ratio appropriately so that ...

geometry
complement of angle X=90-X supplement of angle X=180-X => complement (C) =supplement (S) -90 C+S=126 C+(C+90)=126 2C=126-90 Solve for C and hence X.

math
Given R=6400 km arc=Rθ The first leg is equi-latitude at 40N with a meridian difference of θx=(38-22)=16° Distance travelled =Rθx cos(40) =6400*(16*π/180)cos(40) =1369.09 km The second leg is along a meridian with a latitude difference of θy(40-...

Math
height : shadow = 25 :15 = 40 : X? Cross multiply to get X=40*15/25=24 m

Physics 1
See related questions, for example: http://www.jiskha.com/display.cgi?id=1350232603

Chemistry HELP! CONFUSED!
First write the equation of the reaction: reactants: NaHCO3+CH3COOH products: CH3COONa+CO2+H2O From the molar masses of NaHCO3 = 23+1+12+3*16 = 84 CO2 = 12+2*16 = 44 We find the stoichiometric ratio of the two compounds to be 84:44 (approximately) Hence by proportions/ratios, ...

Statistics
Assuming probabilities work evenly for 30 times, then you would have won the \$5 prize 30*0.15=4.5 times, with a total value of 4.5*5=\$22.5 while paying \$30 to play. So your expected winning (for one play) is 22.5/30-\$1=0.75-1=-\$0.25 i.e. you expect to lose 25 cents each time ...

Engineering
If you substitute any of the four answer choices into the equation: (y-2)^3=(y+2)^3 you will find that none of them is a good answer. So I suspect there is a typo for the question. The equation as shown above can be solved by assuming y=a+bi Expand both sides to give 12b^2-...

maths
Area of the (orange) right triangle =(3*4)/2 =6 units Area of the rectangular board =20*15 =300 units Assume that 1. a dart always falls within the rectangular board 2. the probability of hitting anywhere in the rectangle is equal then the probability of the dart striking the ...

chemistry
In chemistry, since there are more than 26 elements, some elements are represented by two letters of the alphabet. The first (or the only) letter of an element is ALWAYS written in capital letters to avoid confusion, since formulas of compounds are written without delimiters. ...

Math
Work from inside the parentheses, (g(f(3x))' for x=1 =(g(f(3(1)))' =(g(f(3))' =(g(2))' [from table] =g'(2) =5 [from table]

math
Assume "store one year" means 365 box-days and not "a year or part thereof". k=320000 boxes/year = 320000/365 boxes/day = 876.7 boxes/day If supplies are produced every n days, then it must produce nk boxes at each production, and storage requirements are P...

Geometry
What does [ABCD] represent? If it is the area of the kite, then we know that the area of a kite is the product of the diagonals ÷ 2. Note: You are fully expected to draw a duly labelled sketch in order to follow the following explanations. So AC*BD/2=60 AC*BD=60*2=120 ...

computer,science, java
See http://www.jiskha.com/display.cgi?id=1483264139

mathematics
For a (complete) sphere, volume=(4/3)πr³ The volume of material is the volume of whole sphere (radius r2) minus the volume of empty spherical space (radius r1). The thickness t is the difference between r1 and r2, i.e. r1+t=r2. Vm=(4/3)π(r2³-r1³) The ...

Math
Area of a rectangle = Length * width (or breadth) = L*W Take out your calculator to calculate the product. For someone who has done factoring, 11.5*12.5 =(12-.5)(12+.5) =12²-0.5² =144-0.25 =143.75 without using a calculator.

math
We know that diagonals of parallelograms bisect each other. Using this fact, we would draw two intersection lines with an included angle of 60° (and 120°). From the intersection, measure out four vertices 5/2=2.5 cm on each side of one line, and 7/2=3.5 cm on each side...

science
suggested approach: create a class for each Employee, with class properties as integer code string name double salary char category double bonus double totalSalary with class methods called double calculateBonus() void printEmployee() Use switch-case to calculate bonus. Add ...

physics
The most important part of answers of this type of physics problems is the assumptions made to arrive at the answer. With a given answer, these assumptions are usually given, but not in the present case. The given answer corresponds to the following assumptions: 1. D>>H ...

ChemistryStociometry
1. Calculate moles of CoCO3 =6.0/(58.933+12.0+3*16.0) =6.0/118.9 =0.0504 mol 2. Calculate moles of HCl =40/1000*2.0 mol =0.080 Using stoiciometric ratios CoCO3 used = 0.08*1/2=0.04 mols => CoCO3 is in excess (<0.0504). The remaining answer can be obtained by finding the ...

Math
Principal and interest after 8 months =8000(1+0.0276/12*10)=8184 Let a=initial repayment amount (n=1), then the repayment amount at month n a(n)=a*r^(n-1) where r=2 Total repayment amount Sum=a(1)+a(2)+...+a(10) =a(r^10-1)/(r-1) =1023a Equate total amount owing with amount ...

math
Do you mean volume=54 dm³ ? Use 1 dm³=1000 cm³ volume=length*width*height and solve for height.

chemistry AS
Analyse the name piece by piece. Pentene = a 5-carbon hydrocarbon with a single double bond. Pent-2-ene has a double bond in the second carbon atom. (Z) at the beginning means that the two CH3 groups are on the same side of the double bond (Zusammen) means "together"...

Math
The rebound height is a geometric sequence, i.e. H(n)=H0*r^n where n=number of bounces. For H0=16', r=0.25 H(1)=16*(0.25)^1=4' H(2)=16*(0.25)²=1' ...

Fun Physics
Yes, I did it differently, and this time I can eliminate all other variables. I get 0.06 m/s only if the final speed has been reduced by 0.59 of the original speed. If the final speed is 0.59 of the original speed, then μ=0.1396. Let: t=theta=16.1° g=acceleration due to...

Fun Physics (to Rose)
It's an interesting problem. Do you happen to be given the initial velocity as 0.7 m/s ? I have an impression that μ is dependent on the initial velocity.

maths
Propagation value of variable is a very useful iterative method for solving system of equations, especially if certain variables have constraints. The given example is especially favourable example for the method because the coefficients are diagonal dominant. We rewrite the ...

discrete mathematics (to yopo)

discrete mathematics
Number of arrangements of n persons in n positions is n!. Example, 3 people, 3 places, there are 3!=6 possible arrangements. a) If Syahirah mush be in the third position, there are 5 people left for 5 places. Use the formula above. b)If Dinesh must be second, and Felina third...

Statistics
How many are in the family?

algebra (to Rehan)
Please check your own posts and "related questions" before reposting. This is the sixth post of the same question in the last 50 hours, answered by 5 different tutors.

math
This question has been answered 4 times in the last 50 hours. The links are the first four under "Related Questions" below. It is always to your advantage to go through the "Related Questions" before you even press the "Post Answer" button. Also, ...

maths
a shorter way. 1/sin(x)+1/cos(x)=2√2 multiply by sin(x) on both sides, 1+tan(x)=2√2 sin(x) square both sides (1+tan(x))²=8sin²(x)=8tan²(x)/sec²(x) using 1+tan²(x)=sec²(x), (1+tan²(x))(1+tan(x))=8tan²(x) set t=tan(x), and ...

maths (to Steve)
Nice thought! Thank you!

maths
Perhaps there is an easier way to solve this problem, but this is all I have for now. Where there is no confusion, sinX=sin(x), cosX=cos(x) We'll work on the left side first cscX+secX =1/sinX+1/cosX =(cosX+sinX)/(sinX*cosX) =2(cosX+sinX)/sin(2x) [use sin(2x)=2sin(x)cos(x...

MATHS
Clock runs 10 minutes fast every 24 (real) hours. So clock shows 24*60+10=1450 minutes after 1440 minutes. 3PM-10PM=2+15 hours = 17 hours = 1020 minutes. Actual time passed from 10PM = 10pm + 1020*(144/145) =10 pm + 1012 28/29 minutes =14:52:57.93

Computer Science
If you know the ascii code, 48-57 0-9 65-90 A-Z 97-122 a-z Most of the remainder (0-127) are special characters, except space (32) and perhaps other white space characters. It will consist of one while loop to check each of the above. For the extended ascii table, see http://...

Math(A.P)
You're welcome!