Saturday
October 25, 2014

Posts by MathMate


Total # Posts: 10,750

algebra
Fractions have implicit parenthese around the denominator and numerator. I have a feeling that the two log3 terms both belong to the denominator, in which case the expression should have been written, according to the BEDMAS rules, (2*log7 16)/((log3(√10+1)+log3(√...
May 18, 2014

Chemistry
When temperature remains constant, use Boyle's law: PV = constant, or P1V1=P2V2 Also, for conversion, use 1 atm = 101.325 kPa
May 18, 2014

Chemistry
Use ideal gas law: PV=nRT (T in °K) => P=nRT/V =1.3 mol *0.0821 L atm °K-1 mol-1 *(22+273.16)°K/13 L =2.423 atm =2.4 atm (approx.)
May 18, 2014

chemistry
Use c1v1=c2v2 c1=230 g/L c2=200 g/L v2=2 L Solve for v1. Water to be added equals v2 - v1=2L - v1
May 18, 2014

Physics
Use the kinematics equation: Δy = viΔt + (1/2)gΔt² Here Δy=-25' vi=0 (initial velocity) g=-32.2 ft/s² Δt=√(2Δy/g) =√(2*25/32.2) =1.246 s. (approx.) Velocity =1.246*(-32.2) fps =40.12 fps =40.12/5280*3600 mph =27.4 ...
May 17, 2014

math
In the Cartesian plane, +x-axis is to the right, -x is to the left. Similarly, +y is up, and -y is down. For example, a translation of 2 units to the left and 3 units up would be written as (x,y)->(x-2,y+3) so a point (5,3) would become (3,6). Apply the same logic to the ...
May 17, 2014

c++
If you could use further help, post what you've got so far, and we'll take it from there.
May 17, 2014

Degree symbol
The degree symbol (°) may be written (at this forum) as the following, with all spaces suppressed: & d e g ;
May 17, 2014

physics
Assuming question wants height of table, Δy. Use kinematics equation: Δy = viyΔt + (1/2)gΔt² Assuming 1.1m/s is horizontal velocity (slides off table), so viy=0 g=-9.8 m/s² Δy=0+(1/2)(-9.8)(0.35²) =-4.9(0.35²) =-0.060 m Floor ...
May 17, 2014

Math -___-
Detailed explanation on how to make a stem and leaf plot. Difficult to show without fixed format characters. http://www.purplemath.com/modules/stemleaf.htm
May 17, 2014

physics
Use Newton's second law: F=ma=100000kg * 2 m/s² = 200000 N
May 17, 2014

Science Physics
Similar to previous problem of crate. Use Newton's second law: F=ma where F is net force=applied - friction.
May 17, 2014

Science Physics
F=160 N m=20 kg Ffr=80 N Net force causing acceleration = 160-80 =80 N Use Newton's second law, F=ma a=F/m =80/20 =4 m/s²
May 17, 2014

Algebra
At vertex, x=6/10=0.6 Try f(-1)=-2 f(0)=9 f(2)=-1 So -1 and +2 could be approximate zeroes of f(x).
May 17, 2014

UOS
Pseudocode: read Capacity, MilesPerGallon MaximumRange:=Capacity*MilesPerGallon print "Maximum Range = ", MaximumRange
May 17, 2014

CHemistry
First calculate molecular masses of MH2 = (2*1.008) and MH2O = (2*1.008+15.999) Then mass of hydrogen produced =mass of water *(MH2/(2MH2O)) Note the factor 2 in the denominator comes from the stoichiometric coefficient of H2O.
May 17, 2014

Math
The answer to the question as posted is n=942!/(15), which is a large number approximately equal to: 1.45*10^2393. I suspect the factor 15n should read 15n. If that's the case, I offer the following. 942! is the product 942*941*940*....3*2*1 If n=1, then 942!/(15) should ...
May 17, 2014

Math
There are 20 yellow x green 80-x pink Total 100 P(YP)=(20/100)(80-x)/99 P(GY)=(x/100)(20/99) If P(YP)=P(GY) then 20(80-x)=20x after cancelling identical denominators Solve for x: x=1600/40=40 So there are 40 green and 40 pink mints. If P(YP)>P(GY) then 20(80-x)>20x 40x&...
May 16, 2014

Physics
1. calculate distance travelled before brakes have effect. 2. Once deceleration of 10 m/s² starts, car decelerates at that rate. Time taken to decelerate = initial velocity / 10 m/s² = 2 seconds. 3. Calculate distance travelled during those two seconds: vf²=vi&...
May 16, 2014

Algebra
I think the formula should read: h=-16t^2+vt+s Where s=initial height = 25' v=initial velocity = 96 fps t=time in seconds -16=half of acceleration due to gravity in ft/s² so the equation becomes h(t)=-16t²+96t+25 solve for t when h(t)=0.
May 16, 2014

physics
Time, t, to reach ground = Δx/vix = 2.329 s Use kinematics equation Δy=viy*t+(1/2)g(t)² = 10.92 m. (g=-9.81 m/s²), viy=0)
May 16, 2014

math(urgent)
Interest earned was simple interest, so in two years, the future value is 1000(1+2*0.1)=1200 With compound interest of rate i, the equivalent interest would be 1000(1+i)²=1200 or (1+i)=√(1200/1000)=1.095445 or 9.54% approx.
May 16, 2014

math
I think you mean "...from A to A'". Without the accompanying figure, every answer can be correct. You can figure it out as follows: Measure the horizontal distance between A and A', see if A' is to the left by 9 units of A. Similarly, check if A' is 3...
May 15, 2014

physics
Use conservation of momentum: m1u1+m2u2=m1v1+m2v2 m1=m2=0.5 kg u1=10 m/s u2=0 m/s v1=1.5 m/s Since m1=m2=0.5 kg, the masses can be cancelled out to give u1+u2 = v1+v2 10+0 = 1.5 + v2 v2=8.5 m/s
May 15, 2014

math
Agree! Please continue if you have a question.
May 15, 2014

geomettry
The first vertex is at 0° with the x-axis. The other vertices are at respectively θ= 60, 120, 180, 240 and 300° with the x-axis. The corresponding coordinates are at: ( 8cos(θ), 8sin(θ) ) Example: At θ=0° the vertex is (8cos(0°), 8sin(0&...
May 14, 2014

NO SCHOOL
Goods and Services Tax (applies to all Canada). Some provinces combine with the provincial sales tax to call it Harmonized Sales Tax (HST). Assume $100 includes GST, then the GST portion is $100*(10/110)=$100/11. If the GST rate is 15%, then the GST portion will be $100*(15/115).
May 14, 2014

Math
Increase per year = $900 Target=$65000 current amount = 3000 Number of years to generate exactly 65000 =(65000-3000)/900 = 68.89 years So minimum number of years to equal or exceed target = 69 years (a little more than "several" years!)
May 14, 2014

Chemistry
Heat, Q =mcΔT =1200*4.184*(86-24)° =... joules Divide by 1000 to convert to kj.
May 14, 2014

maths
I think you mean: In a triangle PQR. q=8cm , r=6cm . Cos(P)=1/12. Calculate the value of p. where capital letters mean vertices, lower-case letters mean lengths of sides opposite the corresponding vertex. Use cosine rule: p²=q²+r²-2qr(cos(P)) and solve for p.
May 14, 2014

route surveying
1 mph = 5280*.3048/3600=0.44704 m/s vi=50*.44704=22.352 m/s vf=0 a=-10 m/s² use kinematics equation vf²=vi²+2aΔx to solve for Δx. Subtract Δx from 80m to get the distance from the wall.
May 14, 2014

Math
z+7+5=4 or 14, so z=2 4+2+x+1 (from carry)=1 or 11, so x=4 0+0+1 (from carry) =y so y=1 x=4, y=1, z=2 What is xyz?
May 13, 2014

french
Jenna, In French, every accent counts, as well as capitalization. For example, "Ce concert est très ennuyeux."
May 13, 2014

math/probability
With replacement: P(BY)=P(B)*P(Y)=(6/21)*(7/21)=2/21
May 13, 2014

Physics
Without friction and air resistance, we equate potential (PE) and kinetic (KE)energies. Energies at bottom of hill = energies at top of hill. 0+(1/2)m*vi²=mgh+(1/2)m*vf^sup2; cancel m and substitute g=9.8 m/s² vi=20 m/s h=15 m (1/2)(20²)=9.8*15+(1/2)vf² ...
May 13, 2014

Math
Amount = Pert where P=principal, present value so 225500=Pe.0865*(8+125/365) solve for P to get: 109585 (approximately)
May 13, 2014

physics
Initial volume of liquid, V = 3.5 × 10-4 m³ Change in temperature, ΔT =(78-5)=73° Spillage, ΔV =3.6 × 10-6 m³ Coefficient of volume expansion over that of the can =(ΔV/V)/ΔT =(3.6*10^(-6)/(3.5*10^(-4)))/(78-5) =1.4090*10^(-4) ...
May 13, 2014

Calculus
This sounds like a physics problem: Work done = increase in potential energy (PE) Let PE at ground = 0 After lifting, the centre of gravity of the chain is at h=10 m above ground, so potential energy =mgh =(3 kg/m * 20m)*9.8 m/s²*10m = 5880 joules Using calculus, Let &rho...
May 12, 2014

MATH 1 QUESTION PLS HELP ASAP!!!!!
The given expression is a geometric progression, which means that successive terms are obtained by a constant multiplier. If you look at the quotient between successive terms, (a) does not even give a constant ratio, so (a) is out. For (c), there is a problem with the first ...
May 12, 2014

pre cal
Read from the following table: https://www.stat.tamu.edu/~lzhou/stat302/standardnormaltable.pdf You will see that 2.275% of data falls beyond μ+2σ and another 2.275% of data falls below μ-2σ.
May 12, 2014

algorithms
Algorithm of sorting exactly three object, a,b,c is like comparing masses of three objects on an ungraduated balance. if a>b then _if b>c then __a>b>c _else if a>c then __a>c>b __else __c>a>b else if a>c then __b>a>c _else if b>c then ...
May 12, 2014

Physics HELP!!!!!!!!
Oops, the reduction in volume is 41.1%, so ΔV=1.933 *10^-4 m³ and work done, W=22.4*0.021/1000*0.411*101300 =19.58 j =20 j (approx.)
May 11, 2014

Physics HELP!!!!!!!!
To get work done in joules, use metres, Pa, and m³ as units. Volume at 0° and 1 atm for n=0.021 V= 22.4*0.021 L = 4.704*10^-4 Pressure 1 atm = 101.3 kPa = 101300 Pa ΔV =0.41V =1.929 *10^-4 Using Work=PΔV, =101300*1.929*10^-4 = 19.54 J = 20 J (approx.)
May 11, 2014

(2-8) Chemistry - Science (Dr. Bob222)
For B, think of the ideal gas as a compressed spring. When the compressed spring expands, it does work on the surroundings. The external pressure has to stay constant to ensure work is done. If the external pressure decreases, the system can expand without doing any work.
May 11, 2014

ALGEBRA
I suspect the equation should read P = 14.7e-0.21a in order that the pressure decreases with altitude. For P=13.29 13.29=14.70.21a e0.21a = 13.29/14.7 take log on both sides -0.21a = ln(13.29/14.7) a=-ln(13.29/14.7)/0.21 = 0.4802 miles = 2535.3 feet (approx.) = 2535 feet (...
May 11, 2014

Physics
m1u1+m2u2=m1v1+m2v2 12*15+36*5=12*6+36*v2 Solve for v2.
May 11, 2014

math
effective rate =(1+i/n)^n - 1 where n is the number of compounding per year. For 7% compounded semi-annually, n=2, and i=0.07 effective rate =(1+0.07/2)²-1 = 7.1225%
May 11, 2014

Chemistry help
Think of some of the energy released has been used to transform water(l) to water(g) and adjust accordingly. Watch the stoichiometric coefficient of H2O.
May 11, 2014

Calc
Oops, I got the function wrong, got an extra t on the right hand side. Go with Steve's solution.
May 11, 2014

Calc
dy/dt=-0.15y dy/y = -0.15t ln(y)=-(0.15/2)t²+C f(t)=y=Ce-0.075t^sup2; At t=0, y=3 ml. f(0)=C=3 so, let t=time for second dose, f(t)=3e-0.075t^sup2; solve for f(t)=1 ml. -0.075t²=ln(1/3) t=sqrt(-ln(1/3)/-0.075) =3.8273 (approx.) Time for third dose (after second dose...
May 11, 2014

chemistry
Convert 811 cg to kilograms 811.0 cg = 811.0/100 g = 8.110/1000 kg =0.008110 kg Then use formula to calculate concentration in ppm. Keep the answer to 4 significant figures.
May 11, 2014

chemistry, first year university
Assuming the temperature was at STP (0°C). Consider a 1-L volume. Total pressure = 421959.129Pa = 421.96 kPa = 4.1654 atm at 0°C Partial pressure of each product = 2.08272 atm This implies PN2=PH2 =2.08272 atm Kp=PN2²PH2² = 2.0827^4 = 18.8158475075608 = 1.882...
May 11, 2014

chemistry
oops! The example reaction should read: HCl + H2O -> H3O+ + Cl-
May 11, 2014

chemistry
Ionization of an acid in water is typically the formation of hydronium ions, H3O+ and the associated spectator ion. Example: HCl + H2O -> HH3O+ + Cl- (A) Hydrobromic acid: HBr It is very similar to ionization of hydrochloric acid above. For the rest, the reactions are ...
May 11, 2014

Science help please
Hints: Trachea is a part between the throat and the lungs. The alveoli perform the major function of the respiratory system, namely exchanges intake of fresh air (O2) with waste carbon dioxide (CO2). They are also the ultimate destination of intake of fresh air.
May 10, 2014

Physics
Note: the degree symbol is written as & d e g ; (suppress all spaces) Difference in elevation, Δh = 270m × sin(6.5°) total mass (cyclist + bicycle), m = 95 kg total weight = mg Work done (on cyclist & bicycle) =mgΔh Component of force along slope, F = mg ...
May 10, 2014

Physic
Assume diver is 8.2 m below surface (and not 8.2mm), and at the surface, P=101.3 kPa. Pressure below surface =ρgh =1000 kg/m² * 9.8 * 8.2 + 101.3 = 80.36+101.3 kPa = 181.66 kPa Assuming temperature below water and at the surface are identical, use Boyles law: P1V1=...
May 10, 2014

calculus
Unless I am mistaken, the paraboloid looks like a mountain, tapering off to zero along a circle of radius 3. The cylinder has a radius of 2 and its axis is along the z-axis. So the volume of the paraboloid outside the cylinder is like you drilled a vertical hole of radius 2 ...
May 10, 2014

calculus
First find out where z(x,y) intersects the x-y plane, which turns out to be a circle given by x²+y²=9 So you would need evaluate the volume of the paraboloid above the x-y plane between the circles x²+y²=2² (cylinder, radius = 2) and x²+y²=3&...
May 10, 2014

Plz, check my answers.
#1 is not correct. Breaking down large molecules into smaller ones helps the body absorb nutrients from different kinds of food. #2 The circulatory system has the main function of collecting carbon dioxide excreted by cells in different parts of the body and exchange for ...
May 10, 2014

Science
1. incorrect Food gets digested in the stomach, and nutrients absorbed in the small intestine, and finally excess water extracted in the large intestine. 2. Not sure about the "two servings", and the left and right. 3. incorrect. It is used for grinding hard food, ...
May 10, 2014

Science-3 question
#1 incorrect. Question asks which function is not one of the circulatory system. #2. incorrect. Blood has the dual function of supplying oxygen to different parts of the body and also to exchange excreted carbon dioxide with oxygen of fresh air. #3. correct.
May 10, 2014

Engineering skill
Are you able to understand the problem without the accompanied plan/sketch? If you can, kindly describe what you understand in words, or post a link to the plan. Thank you.
May 10, 2014

physics
Since the question asks for time in the air and distance from the building, we will use vi (initial velocity) as a parameter, and solve accordingly. Assume: '=feet fps=feet per second g=32.2 m/s² vi=initial velocity in fps Horizontal component of velocity, vih =vi cos...
May 10, 2014

physics
What are being asked depends on the initial velocity. Do you know the velocity, or you are expected to come up with an algebraic expression in terms of the initial velocity? Is the ball thrown at 60° above the horizontal?
May 10, 2014

Algebra 2
an=8n Substitute n=1,2,... a1=8*1=8 a2=8*2=16 ... guess you can take it from here.
May 10, 2014

physical
Write "brake", and "braking" when stopping a car. m=2500 kg vi=25 m/s vf=0 t=20 s vf=vi+aΔt 0=25+a(20) solve to get a=-25/20=-5/4=-1.25 m/s² Use Newton's second law to get force force, f = ma =2500 (-1.25) N =-3125 N Ignore the negative sign ...
May 10, 2014

Math (Calculus)
The challenging part of this problem is to find the limits of integration, which is the intersection of the two curves. As a hint, they meet at x=1.9 and 4.5 (approximately. You can use Newton's method or other iterative methods to improve the solutions. After that, the ...
May 9, 2014

Algebra
Ratio of 80% and 30% acids is 62-30:80-62 =32:18 =16:9 To make 50 L of 62% Volume of 80% acid = 50*(16/25)=32 L Volume of 30% acid = 50*(9/25)=18 L
May 9, 2014

Calculus
For #1, y′= x(1+ y) write y'/(1+y) = x put p=y+1 p'/p = x ln(p) = x²/2 + C p=ex²/2+C y=ex²/2+C-1 =Cex²/2-1 or =Cex²/2
May 9, 2014

calculus-answer check
Oh, sorry, I had the two terms divided and not multiplied.
May 9, 2014

calculus-answer check
I do not have the same value as yours. Can you post the derivative?
May 9, 2014

physics
Newton's second law: F=ma if F and m are both identical, the a would be the same, where a=deceleration in m/s². Using the kinematic equations for the first car, vf²=vi²+2aΔx vf=final velocity=0 vi=initial velocity Δx=stopping distance and solve ...
May 9, 2014

ALGEBRA
Not sure what your choice is, and also if the actual question should read: Y(x)=sqrt(x+4)-3 or Y(x)=sqrt(x+4-3) [as you had it] Can you check if there is a typo?
May 9, 2014

ALGEBRA
I suppose you mean Y(x)=sqrt(x+4)-3 in which case you can evaluate the function for the various given values and see which one, if any, gives Y(x)=0.
May 9, 2014

Chemistry
[H3O+]=10-4.67 = [BrO-] [HBrO]=0.200-10-4.67 Ka=[H3O+][BrO-]/[HBrO]=2.286×10^(-9)
May 9, 2014

Physics
Assuming the "semicircular shape" is like the loop of a roller-coaster, and we want the body to complete the circle. At the top of the loop, of diameter d (radius d/2), the velocity must be such that the centripetal force exerted by the rails ≥0, or mv²/(d/2...
May 9, 2014

Physics
Assuming the first sentence to mean: "A 10kg box is initially at rest on top of a hill 10m above the ground level." I.e. the box is resting at the top of the hill, which is 10 m. above ground level below. Using ground level as zero potential energy, then At top of ...
May 9, 2014

Physics
Does the missing figure show the mass of the ball? There is centripetal force of magnitude mv²/r (horizontal) and the weight (vertical) of mg to form the resultant tension of the string of 7.7N. r is the horizontal radius, so must be adjusted for the angle the string ...
May 9, 2014

Economics & Statistics
20 represents the slope. Slope is defined as the increase in y-value divided by the increase in x-value, that is: slope = Δy / Δx
May 8, 2014

math probability
1/11 is correct. We can do it in two different ways, easy and difficult. Easy way: Pick 2 of the 5-marbles and any of the remainder. 2/12*1/11=2/132=1/66. The two 5-marbles can be arranged in 4P2 = 4!/(2!2!)= 6 ways, so probability = 6* (1/66) = 1/11 The difficult way: We ...
May 8, 2014

Physics
Correction to equation (a) W=kx^2 ÷2 (watch units) (b) use same equation, with W=50 ft-lbs = 600 ft-in. solve for x.
May 8, 2014

Physics
(a) W=kx^2 (watch units) (b) use same equation, with W=50 ft-lbs = 600 ft-in. solve for x.
May 8, 2014

Chemistry - Science (Dr. Bob222)
Some of the heat generated would have been diverted to convert 2H2O(l) to 2H2O(g), so heat generated would be reduced by 2*40.7=81.4 kJ/mol. Can you take it from here?
May 8, 2014

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

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