Wednesday
August 24, 2016

Posts by MathMate

Total # Posts: 11,475

algebra
Factor x²-6x+9=64 x²-6x+9-64=0 x²-6x-55=0 the factors of 55 are 11 and 5 the difference of which is 6, so try (x-11)(x+5)=0, and it works. This the solutions of the equation are {11,-5} Check: (11^2-6*11+9=64, so 11 is good. Check the same for -5.
June 22, 2016

Math
Given: radius=7cm Circumference=perimeter of rectangle Ratio of breadth:length = 4:7 Let b=breadth, then length=(7/4)b circumference=2π(7)=14π circumference=perimeter therefore 14π=2(b+(7/4)b) 14&;i;=2(1+7/4)b (11/2)b=14π b=14π(5/11)=7.997=8 cm approx. Check: ...
June 17, 2016

Geometry
o 6 o o o 5 o 7 o o o 8 o The sum of the four angles equals 360°. ∠ 5= ∠ 7 (vertically opposite angles) Similarly ∠ 6= ∠ 8 (vertically opposite angles) Sum of the four angles ∠5+∠6+∠7+∠8=360° 2( 2x+15 + 3x) = 360° solve for x and ...
June 17, 2016

Math(Scale Factors and Scale Diagrams)
The game is 1/4 of the wanted size, so each of the dimensions of the wanted sized table is four times as big. For example, if he wanted a size twice as big (scale factor = 2), then the dimensions are 2*(9 1/4) × 2(4 15/16) = 18 1/2 × 9 7/8
June 16, 2016

CALC
Let f(x)=2x-tan(0.18x) the area required is given by integrating, ∫(2x-tan(0.18x))dx for x=1 to 5. How did you come up with a value of 9? Please show your work so we can help you correct the steps. As a rough estimate, we can see that f(1)=1.81 f(5)=8.74 And it is a ...
June 16, 2016

Algebra, please help
5x+3y=7 ...........(1) 3x-5y=-23 .........(2) We try to cancel/eliminate one of the variables. I choose to eliminate y. 25x+15y=35 ...........5*(1)....(1A) 9x-15y=-69 .........3*(2).....(2A) Add (1A)+(2A) 34x=-34 Solve for x. Substitute value of x into 1 and solve for y.
May 26, 2016

Maths
P=2950 (principal) i=0.081 per month (period=1 month) n=18 (periods) A=P(1+i)ni (accumulated value) Take out the calculator and calculate the value of A, value after 18 months.
May 24, 2016

Physics
We don't see the diagram, but assume that the cart is at the beginning of an uphill slope of angle θ with the horizontal. The problem comes to a matter of conservation of energy, since friction is neglected. Kinetic energy of the running boy KE= (1/2) mv²=(1/2)...
May 24, 2016

Algebra 1B Radical expressions & data analysis
I think you meant: #4 6/(√3 + 2) #5 y = 3√(6x + 42) #6 y = 2 √(3x + 4) - 5 #7 y = √(x+4) - 3 Note that a space does not imply parentheses, which are very important in mathematics. Read, for example: http://www.mathgoodies.com/lessons/vol7/...
May 23, 2016

BIO PLEASE HELP!
Try reading carefully the following link: http://www.microbeworld.org/types-of-microbes/protista
May 13, 2016

Biology
See your other post.
May 13, 2016

Probability - marbles
8 black and 7 green in urn (15 in all) 5 drawn with replacement. Probability that first one is green: P(1)=7/15 Probability that second one is green P(2)=7/15 (ball is replaced) ... P(5)=7/15 For all 5 steps to succeed, multiply together the individual probabilities P(all five...
April 21, 2016

Math
A number is rational when it can be expressed as a fraction of integers. For example, 24 is rational because 24=24/1=48/2... -3 is rational because -3 = -6/2 = -3/1 .... So see if you can figure out if -49 is rational.
April 21, 2016

Physics
height, h=135*16 cm = 21.6 m Time taken, t= 5 min 40 sec = 340 seconds mass, m= 63.9 kg g=9.81 m/s² (note that all values are in SI units) Work done, W = mgh J (joules) = 13540.2 J (multiply together m,g & h to get work done) Power = work done per second, so = W/t J/s =...
April 19, 2016

algebra
Cats have 4 legs. Budgies have 2 legs. Two ways to do it: 1. use algebra. C=no. of cats 3C=number of budgies total number of legs 4(C)+2(3C)=30 10C=30 C=30/10=3 So 3 cats and 9 budgies. Check: 3*4+9*2=30, checks. 2. by guessing We don't know how many of each, make a guess...
April 19, 2016

ns
This is spam.
April 19, 2016

statistic
Step 1 initially there are 20 students of which 6 have blue eyes. Probability of choosing the first with blue eyes is 6/20. Step 2 There are then 19 students left of which 9 have brown eyes. Then the probability of choosing a brown eyed student is 9/19. Since it is a two-step ...
April 19, 2016

computer science
pseudocode: x=input package name, x=1 for A, etc. n=input number of hours ... cost=0 if x=1 then cost=9.95+min(0,2*(n-10)) else if x=2 then cost=13.95+min(0,1*(n-20)) else if x=3 then cost=19.95 else print "incorrect package" endif print x, n, cost
April 18, 2016

calculus
Very cute problem. The answer is as cute! Look at the table shown in: http://prnt.sc/atvi6m f(x) and f'(x) are given on the third row! If you are in an exam, your teacher may not appreciate the "cute" answer. So let's work it out: f(x)=1/(1+(1/(1+(1/x)))) If ...
April 18, 2016

friction & centripetal force
Given: r=4.5 m angular velocity ω=2*π/7.2 rad/s =0.8727 rad/s When the cat is at position of 3 or 9 o'clock, the horizontal acceleration due to centripetal force is at its maximum. The centripetal acceleration is a=rω² The centrifugal force is F=ma=mr&...
February 18, 2016

Math
The logical solution is to take away 3 from 27 and divide by two to give the smaller number. Then add 3 to get the bigger number. Check by adding the two results to see if they add up to 27. If you have to use system of 2 linear equations, then let x=smaller number y=larger ...
February 18, 2016

Finance
Oops! Good catch! Thanks. Elcia, please go with Reiny's answer.
February 18, 2016

Finance
Use the mortgage formula: Future value = FV = 1000000 payment per period = P (to be found) rate of interest (per period) = i (0.06/12=0.005 per month) R = 1+i = integrated rate = 1.005 n = number of periods = (55-28)*12=324 then FV=P(1+R+R²+R³+....+Rn-1) =P(R^n-1)/(R...
February 18, 2016

Math Help
Yes, they are correct! I didn't notice you gave answers, sorry.
February 18, 2016

Math Help
For question one, you need to look at each number (of eight digits) which represents 8 campers. Any digit 0 or 1 represents out-of-state campers. Count how many of the 20 numbers contain at least two of 0 or 1. For example, the first number is 69531217 which means that there ...
February 18, 2016

Math
There are 360° in a whole turn (an hour). So 24 degrees is, by proportion, (24/360)=1/15 of an hour. Add this to 12:59 to get the time.
February 18, 2016

One Math Problem
See help above http://www.jiskha.com/display.cgi?id=1455846917 In fact, we are the ones to ask you for any thoughts!
February 18, 2016

probability
P(diamond)=13/52 P(king)=4/52 To select a diamond and THEN a king (with replacement) is then the product of the two above probabilities.
February 18, 2016

Personal Finance
Front end loading is the commission of a given percentage to be deducted from the total amount invested. Here the percentage is 5.25%. The total amount invested is $20000. The product of the two is the commission (front-end load). See definition of front-end loading: http://...
February 18, 2016

MATH
This system can be solved readily by elimination. You can eliminate y by adding the first equation to twice the second equation. Show us what you get!
February 9, 2016

programming
You need to find n^m where m is the sum of the digits of n. Step 1: Find the sum of digits of n. You could try the following algorithm, either inline or using a function (method): Let k=n m=0 do until k<=0 m+=k%10 k/=10 end do Step 2: Raise n to the mth power: result=1 k=m ...
February 9, 2016

Physics
Take moments about the fulcrum and equate to zero. Solve for F=effort. on the load side: force = 600N distance from fulcrum= 0.5 m On the effort side: force = F N distance from fulcrum= 1.5m - 0.5 m = 1 m. Moment equals force time distance from fulcrum, clockwise positive.
February 5, 2016

Surveying
We have a parabola, and the crown is 6 inches over a 30-foot width, i.e. 15' on each side of the crown. The elevation of the crown is 612.58, and on each side of the road the elevation is 612.58-0.5'=612.08. Taking x=0 at the crown, the equation of a parabola with the ...
February 5, 2016

Calculus
s(t)=t²-6t+5 is the position vector. For example, at time=0 hour, s(0)=5, so the person is 5 miles north of LA, etc. Velocity is the derivative of position with respect to time, namely, v(t)=s'(t)=2t-6 At time t=0, v(t)=-6, meaning he was cycling towards LA. ...
February 3, 2016

physics
So rocket never got propulsion after launch, becomes a projectile. u=92.0 m/s, θ=33° horizontal velocity (constant) ux=u cos(θ) Time to reach wall (in seconds) t1=26.0/ux seconds vertical initial velocity uy=u sin(θ) vertical height at time t sy(t)=uy*t-(...
February 3, 2016

Physics
To find the resultant, resolve forces into x (due east) and y (due north) components and add. Use a diagram to help you understand the angles.
February 3, 2016

physic
The largest value of A+B is when they act in the same direction, and the resultant is the sum of the magnitudes. The smallest value of A+B is when they act in opposite directions, and the resultant is the difference of the magnitudes.
February 3, 2016

Physics
Without the diagram, we're as lost as you are! Is the force F acting up the plane, or down the plane? Is the force F acting horizontally or along the plane?
February 3, 2016

physics
X-component=200*cos(60)+120cos(210) (positive due east) Y-component=200*sin(60)+120sin(210) (positive due north)
February 3, 2016

Physics
Air speed=195 m/s (westerly) Air velocity = 195 m/s (West=positive) wind speed = 53 m/s (easterly) wind velocity = -53 m/s Ground velocity = air velocity + wind velocity = 195-53 = 142 m/s Distance = +276 km = +276000 m Time required = Distance/velocity = 276000/142 s = 1944 s...
February 3, 2016

Physics
1 W/m² is defined as 120 dB. For every 10 dB higher, power is multiplied by 10 times. Inversely, for every 10 db lower, power is reduced (divided) by 10 times. For example, 100 db = (120-20) dB=1W/m²*10^-2 75 dB = (120-45) dB = 1W/m²*10^(-4.5)=10^(-4.5) W/m²...
February 3, 2016

Physics
Use KE=(1/2)mv^2 GPE=mgh where m=mass of plane v=velocity h=height of plane assuming reference plane is ground level. g=9.81 m/s² Use consistent units.
February 2, 2016

Physics please i really need help
For the reaction time, distance = velocity * time = 23.7*0.427 = 10.12 m For the braking time, v²-u^sup2;=2aS v=0, u=23.7 m/s, a=-9 m/s^2, S=(v²-u^sup2;)/(2a) =-23.7^sup2/(2*(-9)) =32.21 m Stopping distance is the sum of the two distances.
February 1, 2016

Physics
Speed = circumference / time Circumference = 2πr = 2*π*5.8*10^10 m = 1.16π*10^11 m Time = 88days * 24h/day * 60min/h * 60sec/min =7603200 s Speed = distance /time = 1.16π*10^11 / 7603200 = 47930 m/s = 47.93 km/s
February 1, 2016

physics
Assuming that the wood block is fixed and stationary. (a) acceleration, a = (final vel. - initial vel) / time = (v-u)/t = (0-16 m/s) / 0.5 = -32 m/s² (b) average force = mass * acceleration = 0.020 kg * 32 m/s² = 0.64 newton (c) Distance, S = ut+(1/2)at² = 16*0....
February 1, 2016

To Soso
See http://www.jiskha.com/display.cgi?id=1454378710 Hope you realize the problem when you post the same problem too many times, ... and not checking answers before reposts!
February 1, 2016

Geometry
For the chord AB k=mXB 2k=mAX We will construct diameter CD such that X lies on CD. Now CX=9+7=16 cm, XD=9-7=2 cm Using the theorem of intersecting chords (AB and CD), we have 16*2=k(2k) Solve for k.
January 29, 2016

Math
Agree with Damon. The only 4 digit number for which 1. all digits are odd, 2. sum of last two digits equal 16 3. divisible by 13 are 7397, 9997, 7579 each of which does not satisfy the requirements 4. digits being distinct, 5. number is less than 3000. However, if the ...
January 19, 2016

math
Solve step by step. Given a 3-digit number. 1. If it is divisible by 5, it must end with a 0 or a 5. 2. If the number is odd, the last digit must be 5. 3. if product of digits is 15, the product of the two remaining digits must be 15/5=3, namely either 1,3 or 3,1. I.e. the ...
January 17, 2016

physical science
momentum=60000kg m/s mass = 2000 kg use relationship momentum=mass * velocity which can be solved for velocity: velocity=momentum/mass
January 17, 2016

FRENCH ! (:
Accents on any keyboard can be done as shown in the following link, for example, & e a c u t e ; stands for é (skip the spaces between & and ;) http://www.starr.net/is/type/htmlcodes.html Other comments: yesterday is hier (not heir). la police et l'ambulance _____ ...
January 14, 2016

Math
When we're dealing with consecutive numbers representing the sides of a triangle, the average of the perimeter (i.e. perimeter/3) is the middle number. Hence find the other two numbers.
January 11, 2016

Behavioral Stat. Lab
Where proprietary software is involved, you have a much better help from your instructor because not everyone here has access to minitab.
January 11, 2016

Math
Student needs to learn the position value of decimal numbers, and that a carry should not shift the digits to the right.
January 11, 2016

Phiysics
use final velocity = initial velocity + acceleration * time Note: deceleration is a negative acceleration.
January 11, 2016

math - typo?
Do you mean: "You need 210 snowballs to make the perfect snow fort you make 15 snowballs in an hour but 10 melt every 15 minutes how long will it take you to make the perfect amount?" Checking your question before you post helps you get your answer fast.
January 10, 2016

Math
If AB is the longest side, then O cannot divide AC and BD in the ratio 1:2 since mAB>mDC. We will use A(BOC) to represent the area of triangle BOC, and so on. Draw a diagram of the trapezoid ABCD with AB//DC and AB>DC. The diagonals AC and BD meet at O. If the division ...
January 10, 2016

science
In the case of a hydraulic lift, the pressure is (almost) identical, so that Force/area is a constant, where area is the area of the respective piston.
January 10, 2016

Science
The keyword here is energy reserves. All except one provide energy, but under different conditions. Discover about all four at the link: http://www.livestrong.com/article/281655-functions-of-lipids-carbohydrates-nucleic-acids-proteins/
January 10, 2016

Science
Ethyl alcohol has a formula of C2H5OH. C8H18 is octane. In any case, you would work out the number of moles of alcohol in 16.5 mL. (note: 16.5 mL*0.789=13.02g) Each mole of alcohol gives out 2 moles of CO2. (Write out the combustion equation). So by proportion, you will get ...
January 10, 2016

MAth 10 (probability
Make a table for the two spins X| 1 2 3 4 --------- 1| 2 3 4 5 2| 3 4 5 6 3| 4 5 6 7 4| 5 6 7 8 Out of the 16 possible outcomes, count how many satisfy the given condition, and divide this number by the number of possible outcomes.
January 10, 2016

Math
We'll first find the limit, and I'll let you continue with the derivative. Let Y=Lim x->∞ (2^x+5^x)^(1/x) =Lim x->∞ ((5*2/5)^x+5^x)^(1/x) =Lim x->∞ ((5^x)(2/5)^x+5^x)^(1/x) [law of exponents] =Lim x->∞ ((5^x)((2/5)^x+1)^(1/x) [...
January 9, 2016

Chemistry-Dr.Bob
Correction: the answer is more appropriately given as 1.54 J/(g-°C) as all the original information is given to 3 significant figures.
January 9, 2016

Chemistry-Dr.Bob
Use ΣmcΔT=0. For metal, mcΔT=100*c*(29-90)=6100c For water, mcΔT=250*4.184*(29-20)=9414 Applying ΣΔT=0 => 100*c*(29-90)=250*4.184*(29-20) Solving for c gives 1.543 J-g-1-°C-1 as you had it.
January 9, 2016

math
It depends on the given information. If base radius (r) and height (h) are given, then angle of cone is given as 2tan-1r/h.
January 9, 2016

math
the parabola y=x² has it's vertex at (0,0). Tangent to parabola has slope dy/dx=2x, at point (±x, x²). For tangents to pass through (0,-25), we have the slope joining (0,-25) and (x,x²) equal to 2x. Slope=(y2-y1)/(x2-x1) => (x^2-(-25))/(x-0)=dy/dx=2x ...
January 9, 2016

French
There is not enough context to give an answer without making assumptions. However, if we assume this is an itinerary for Élaine, the second date (8 days later) could be assumed to be the return (to San Diego) from Marseille, which is reasonable for a tourist. Assuming ...
January 9, 2016

physics
It would appear as homework dumping if you don't show your work. Also, if you make an effort to solve the first one, there is a chance you can apply what you learned to solve the other ones, or at least get a good kick-start. I suggest you review class material, attempt ...
January 9, 2016

Maths
The best way to include a picture is to upload the picture to an image server and post the link. It is not always possible, but give it a try and teachers are likely to help you get it done if there are difficulties.
January 9, 2016

Math
At the beginning, there are 22*760=16720 food days. After 2 days, there are 20*760=15200 food days left. If this should last only 19 days, it will feed 15200/19=80 persons. You can therefore figure out how many more people came (in addition to the original 76).
January 9, 2016

math
Since we are given the hypotenuse and one leg, we can find the other leg using Pythagoras theorem. The area is then the product of the two legs divided by two. Height (of the other leg) =√(3.7²-1.2²)=3.5 Base (given)=1.2 m So you have all information to find ...
January 9, 2016

emmanuel
in a class of ,26 offer mathmatic and 28 offer physics if 8 student do not offer any of the two subject This means that there are 60-8=52 students take at least one subject. Since total number of subjects taken is 26 and 28=54, we know that 54-52=2 students take both. I'll...
January 7, 2016

Math
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January 7, 2016

Geometry
Sum of exterior angles of any polygon is 360°. So if we add up all five exterior angles of the pentagon, we have 2(3x)+2(2x+22)+x+41=360° Solve for x.
January 7, 2016

Statistics
Start with Googling "history of aids" and read up the first 5 or 10 articles. Otherwise, try http://www.avert.org/professionals/history-hiv-aids/overview and http://www.amfar.org/thirty-years-of-hiv/aids-snapshots-of-an-epidemic/
January 6, 2016

Kercy
Most of the time the floating is due to deterioration/decay of the body tissues and gases (CH4, H2S, and CO2) are produced, hence reducing the overall density of the body. Read more about it, for example: http://www.slate.com/articles/news_and_politics/explainer/2005/09/...
January 6, 2016

Math
A dart board has sectors numebered from 1 to 20. We require combinations, so order does not count. Here's how we could proceed: 1. to avoid repetitions, we assume the smallest number is thrown first, then the next smallest, and the largest numeber. 2. There are no limit to...
January 5, 2016

Counting and Probability
Let k=number of 4's to add then E(x)=Σx*P(x) =(8*2+(2+k)*4)/(8+2+k) If E(x)≥3.5 then (8*2+(2+k)*4)/(8+2+k)≥3.5 solve by cross multiplication 16+8+4k≥35+3.5k 0.5k≥11 k≥22
January 5, 2016

partial fraction
step 1: decompose denominator into factors (x³_x²-x-1) =x²(x+1)-1(x+1) =(x²-1)(x+1) =(x+1)²(x-1) Now decompose expression into partial fractions: (Ax+B)/(x+1)² + C/(x-1) = (2x²+7x-1)/(x+1)²(x-1) .....(1) Now match coefficients of powers ...
January 5, 2016

math
What's left is is 100-80=20% So the original amount A can be found by proportions: P100/20%=X/100% solve for X: P100*100%/20%=P500
January 5, 2016

french(le passe compose)
To help you better, I suggest you propose your translation and we will be glad to help you make necessary corrections. For example, (for a male speaker) "I went to school yesterday" would be Je suis allé à l'école hier. Recall that in French...
January 5, 2016

Physics
Hint: read up about Newton's first law, for example, at the following link: http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Newton-s-First-Law
January 4, 2016

physics
Inelastic collision means the two objects do not rebound and move at a common velocity. Yes, choice a is correct.
January 4, 2016

math
*...is related to sign of...
January 3, 2016

math
monotonicity of ln(x) is equal to sign of (ln(x))'=1/x, and domain of ln(x) is D=(0,+∞) Since 1/x is strictly positive for x∈D, so ln(x) is strictly monotonically increasing.
January 3, 2016

physics...perhaps horizontal plane
I assume that the block of mass m=80 kg slides horizontally, and that the force F=400N pushes downwards at an angle of θ=37° below the horizontal. Initial horizontal velocity is u=20 m/s, and we look for velocity v at time t=6 seconds. Further assumption: friction &...
January 3, 2016

Math - typo?
The question as is would provide 3 equations for two unknowns. It would be a good idea to check the question before/after posting.
January 1, 2016

MATHS HELP URGENT(TIME AND WORK)
Fraction of work accomplished W at the end of day t will be denoted W(t). W(0)=0 W(10)=5/6 W(12)=5/6-2/3=1/6 W(22)=1/6+5/6=1 work completed.
January 1, 2016

math
Hint: adjacent angles of parallelgrams are supplementary, i.e. they add up to 180°. For the given problem, if one angle is x, then the adjacent angle is 2x. Since they are supplementary, we have x+2x=180°. Solve for x and hence the angles of the parallelogram.
January 1, 2016

dynamics
Let time t=0 when mass is 3500 and speed is 1220 m/s. then F(t)=500 kN m(t)=3500-80t a(t)=(500*1000/m(t))=acceleration => (i) v(10)=v(0)+∫(500000/(3500-80t))dt for t=0 to 10. =1220-500000[ln(3500-80t)]/80 =1220+1621.945 =2841.945 m/s (ii) using initial mass v(10)=v(0)+(...
December 29, 2015

Math
In four years, the total of the ages will be 46+4+4=54 years. The ratio in four years will be 7:2 So age of daughter in four years = 54*(2/(7+2))=12 age of mother in four years = 54*(7/(7+2))=42 Continue to find their present ages.
December 28, 2015

chem question?answer_to=1210023143
(115 psi)/(14.7 psi/atm) = 7.82 atm assuming the air in the tire has room temperature.
December 28, 2015

physics
Assuming the 10N force is along the positive x-axis. Then the three forces in (magnitude, angle °) are P(10,0), Q(30,120), R(50,240) or in component form: P<10,0> Q<30cos(120),30sin(120)>=<-15, 25.9808> R<50cos(240),50cos(240)>=<-25, -43.301> ...
December 28, 2015

mathematics
Assuming parentheses around the denominator have been omitted, the expression is x²+x+4/[(1-x)(x²+1)] partial fractions for the third term is required, namely 4/[(1-x)(x²+1)] =-4/[(x-1)(x²+1)] =A/(x-1)+(Bx+C)/(x²+1) By adding the right-hand side, we ...
December 28, 2015

Algebra
Constraints: A. x≥0 B. y≥0 C. y-x≤100 D. x+2y≤1400 (please check this constraint) Draw the graph of the constraint equation to have a visual understanding. Solve for all possible corners of the feasible polygon. Note that all inequalities are inclusive, i.e. all ...
December 27, 2015

Math
We know that 5*7=35, so the three digit number probably starts with a 3, and the two digit number starts with a 7. We also know that we should put small digit after 7, and large digits after 3, so the numbers are 384/71 Check: 5 < 384/71=5.408 < 6 There may be other ...
December 26, 2015

stats
Good catch Reiny! I read too fast! To "Help", please go along with Reiny's answer.
December 23, 2015

stats
Yes, that would be correct, because 10+20+30+40=100 so the the probability that she selected French hens would be 10/100.
December 23, 2015

stats
There are 10 French hens. Try to enumerate the number of each kind of pet and then add up the numbers to get the total number of pets. 40 is the number of American chickens.
December 23, 2015

stats
Let success be choosing a French hen out of all possible choices (Ω) and we need to assume the probability of choosing any pet is equal. Probability of success (choosing a French hen) =Number of French hens ÷ Total number of possible choices (&Omega). Here you see...
December 23, 2015

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