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Posts by MathMate

Total # Posts: 11,748

data management gr.12
For (a), you may have double counted some cases, since the total is 1381/1050 >1, whichis impossible.

math
It's almost the same as the silt/soil problem. Let x be the volume of metal in oz needed, then (0.9x+3)/(x+3)=0.92 Solve for x. Do not forget to distribute when you cross multiply.

math
4 cubic ft (cf) of soil contains 4*10%=0.4 cf of silt If we add x cf of silt, total volume = 4+x volume of silt = 0.4+x Given the new percentage is 60%, we have (0.4+x)/(4+x)=0.6 Solve for x by cross multiplication: 0.4+x = 0.6(4+x)=2.4+0.6x transpose and solve for x x-0.6x=2....

math
Let h=height of the box. Then width=120/h length=168/h We know the area of the base is Ab=316 so Ab=width*length, or 316=(120/h)*(168/h)=(120*168)/h². Solve for h h=√(316/(120*168) =12√35/√79. Use the above equations above to find length and width.

algebra
Method 1: Use calculator, and do not forget to surround the numerator and denominator by parentheses, i.e. type in: (9.6*10^2)/(3.2*10^5) Method 2: (easier way) (9.6*10^2) ------------ (3.2*10^5) Note that 9.6/3.2=3, and 10^2/10^5=10^(2-5) =10^(-3) so the answer is 3.0*10^(-3...

Alebra
Example similar to the first one: solve 7x-9>61 Add 9 to both sides 7x-9+9 > 61 + 9 7x > 70 Divide by 7 (on both sides) 7x/7 > 70/7 x > 10 [answer]

HELP ME PLZ MATH
Great!

HELP ME PLZ MATH (to savepuppy)
When we go to the supermarket, with four similar items at different prices and packaging, we need to find the unit price of EACH of the four items in order to determine the best (lowest) unit price. Unit price can be found by the formula unit price = price / number of units or...

Math
1. find Z-score = (X-mean)/stdev =(67-65.5)/(2.5) =(1.5)/2.5 =0.6 2. Look up standard normal distribution tables for one-tail where Z-score = 0.6 P(x<X=67)=0.7257469 [from tables for Z=0.6] For part b, find similarly P(x<X=64) then P(64<x<67) =P(x<67)-P(x<64)

math
ME=Z√(0.25/n) For 90% confidence level, and ME=1% Z=1.644854 [ from tables for two tale at 95%] => 0.01=1.644854√(0.25/n) => n=(1.644854/0.01)^2*0.5 =6763.86 ~ 6764 persons

Algebra
M' means the complement of M. M' will encompass all the elements in the universal set but NOT in the set M. So please give it another try.

Math (1 Question)
The answer is here: http://www.coolmath.com/prealgebra/06-properties/08-properties-multiplicative-identity-01

Algebra 9th
In problems of this type, it is easier if you could make a scatter plot (or dot-plot) of the data before starting the calculations. In case you spot an outlier, you will have to occasion of excluding it before you do the calculations. In the given data, I suspect there is an ...

Financial mathematics
Is this a continuation of the post http://www.jiskha.com/display.cgi?id=1482086783 ? If it is, it would be another advantage to keep your pen name the same (except using anonymous), because otherwise tutors cannot assume continuation and have to ask for details. Is $800,000 ...

Chemistry (to Alice Keign)
morality ≠ molarity lol molarity is the fraction mass of substance contained in 1 L of solution ÷ molecular mass of the substance. Note: atomic mass of Na ~ 23 atomic mass of Cl ~ 35.5 so molecular mass of NaCl ~ 58.5 But you need to look up exact masses from ...

chemistry (To Yasine)
Your effort has a good start, shows you have an idea what's needed, but, to balance equations, you have to know what the possible products are. For example, HO and ZnCl are not known products to me. If you lookup/Google Zinc Chloride, and Hydrogen Oxide, you will find the ...

math(geometric series)
1. find the common ratio: r=T(n)/T(n-1)=12/18=2/3 2. form the general sequence (considering 18 as first term, or n=1) T(n)=ar^(n-1)=18(2/3)^(n-1) 3. solve for T(n)=18(2/3)^(n-1)=512/729 or even simpler, (2/3)^(n-1)=256/6561=(2/3)^8 Solve for n.

math(geometric series)
Sum of a geometric series to n terms with common ratio r is given by S(n)=a(r^n-1)/(r-1). 1. Form the equation: S(20)/S(10)=244 (given condition) 2. Cancel out the common factor a and (r-1). 3. set u=r^10, then r^20=r^2. 4. solve the resulting quadratic in u. 5. Back-...

tangent help me maths
To prove that L1 : 2x+5y+11=0 is a tangent to the circle C : x²+y²+2x-8y-12=0 it is sufficient to prove that the distance of the centre O of the circle C to the line L1 equals the radius of the circle. To find the centre and radius of the circle C, we complete ...

physics (science)
There is a standard formula for this: "from rest" means initial velocity = 0 or V0=0 m/s Given acceleration, a = 8 m/s² S = distance travelled = 100 m Let V1=final velocity, then the given formula is: V1²=V0²+2aS Substitute values of V0, a and S into ...

Chemistry
I do believe that the skill of transforming an actual problem to numbers is part of your training. However, I will work on this for this time. The problem can be solved by proportions. Using: "Therefore 24 g of Mg produces 2 g of H2. How many grams of H2 will be produced ...

Chemistry
The atomic mass of magnesium is 24, which means 24 grams of magnesium makes 1 mole. On the other hand, the atomic mass of hydrogen is 1, so H2 will weigh 2 grams per mole. From part A, which you correctly answered (except for the missing + sign), we conclude that 1 mole of Mg ...

chemistry
Molecular mass of propane (C3H8) = 3*12+8*1 = 44 Molecular mass of water (H2O) = 2*1+1*16 = 18 using the balanced equation, we find that the ratio mass of propane : mass of water = 1*44 : 4 * 18 = 44 : 72 Hence the mass of water can be calculated. Note: replace the above ...

math (to Jose)
hint: 5(S+15)=5*S+5*15 (distribution) =5S+75

Assistance on whether numbers are correct? Financi
To check your answer, 523.23*4*25=52323 which is only about 6% of the final amount, which seems too low. So looking at your working: Future value = (payment)[((1+i)^n-1)/i] is basically correct, if we assume i=interest per period. rate 4.2% is annual interest (by normal ...

Math
C=child ticket A=adult ticket 4C+8A=128 => C+2A=32...........(1) 6A=72 => A=12.................(2) Substitute (2) into (1) C+2(12)=32 solve for C.

SUMMARY OF FINANCIAL TIME VALUE OF MONEY
Part 1: Use the amortization formula: P=(L)R^n(R-1)/(R^n-1) where P=Payment per period L=Loan amount R=1+interest rate per period n=number of periods For example, if monthly payment is required for a 100,000 loan over 30 years at 5% p.a., then L=100,000 R=(1+0.05/12) n=30*12=...

Bayes' Theorem
Agree with the first part, except that with probability calculations, I prefer to work with fractions. If a decimal answer is required, it will be rounded at the end. First Part: P(A)=1/200 P(+|A)=9/10 P(-|A')=1/10 P(+)=P(+|A)+P(+|A') =(1/200)(9/10)+(199/200)(1/10) =13...

MATH
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MATH
A perpetuity payment is a payment received from an initial deposit and annuitized over an infinite period of time. In order for this to happen, each single payment must be equal to the interest generated from the initial deposit (assuming a constant rate of interest). The ...

Calculus Finals Review sheet!! Explanation needed
Next time please number your questions if you have multiple questions. In fact, it is preferable to make separate posts for different questions so that answers and questions will not be confused. If you are referring to the following question: "The altitude of a kite is ...

Stats: Counting Techniques Fundamental Theorems A
number of ways of choosing male employees N1=12C3=12!/(3!9!) number of ways of choosing female employees N2=10C3=10!/(3!9!) Number of possible teams =N1*N2

Check Answer!! Conditional Probability
The idea is sound, but You have the very first step incorrect. In probability problem, it is best to write out the assumptions, so that you AND others who read your text will be able to understand. You have assumed 10000 people in the population, which is ok, but 1/500 of ...

Math
Assuming the question is actually: (n+7)! / (n!(n+6)(n+4))=9!/3 and n>0. First simplify the left-hand side by cancelling n!: (n+7)! / (n!(n+6)(n+4)) =(n+1)*(n+2)*(n+3)*(n+4)*(n+5)*(n+6)*(n+7)/((n+6)*(n+4) =(n+1)*(n+2)*(n+3)*(n+5)*(n+7) So the problem reduces to solving the ...

math
Since we don't have data that Tara has, perhaps a few thoughts will help direct us to the right answer: 1. Does the number of scratches always increase with time? Can it possibly decrease (without changing the windshield)? 2. Assuming the climatic conditions remain more or...

math
Isn't this the answer? "He needs to check the quality of 30% of the sweaters. "

Math - Coordinate Geometry
For the given figure of A(-2,3), B(5,4), C(4, -3) and D(-3, -4). we write it out as, repeating A at the end: A(-2,3), B(5,4), C(4,-3) D(-3,-4). A(-2,3), Find the four products: Ax*By-Bx*Ay=(-2*4)-(5*3)=-23 Bx*Cy-Cx*By=(5*-3)-(4*4)=-31 Cx*Dy-Dx*Cy=(4*-4)-(-3*-3)=-25 Dx*Ay-Ax*Dy...

Math - Coordinate Geometry
sorry, 24 is not correct. one diagonal is 6√2, and the other is 8√2. The product of the two diagonals/2=?

Math - Coordinate Geometry
1. A rhombus is a parallelogram with adjacent sides equal. 2. A rhombus is a quadrilateral with four equal sides. To prove that a figure is a rhombus, use either 1 or 2 above. In this case, proving that the four sides are equal is relatively easy even by visual inspection. The...

Math
μ=np=10 σ²=npq=np(1-p)=9 Solve for n and p. Hint: substitute np in the second equation and solve for p. Hence solve for n.

compute the probability that a person who tests po
Solve using a probability tree: (sick)/0.003*0.9=0.00282 (positive) /0.003\0.003*0.06=0.00018 (false negative) 1 \0.997/0.997*0.02=0.01994 (false positive) (not \0.997*0.98=.97706 (negative) sick) check: .00282+.00018+0.01994+.97706=1.0000 √ "the probability that a ...

Conditional Probability
Note: The numbers in the contingency table can also be obtained by a tree diagram considering a sample of 4000 people. 400--A-->10--B-->9 -------------~B->1 ----~A-->3990--B-->399 --------------~B-->3591

Conditional Probability
Given: P(A)=1/400 P(B|A)=9/10 P(B|~A)=1/10 By the law of complements, P(~A)=1-P(A)=399/400 By the law of total probability, P(B)=P(B|A)*P(A)+P(B|A)*P(~A) =(9/10)*(1/400)+(1/10)*(399/400) =51/500 Note: get used to working in fraction when doing probability. (a) Find P(A|B): By ...

Math
Take out your calculator, or do it by hand, 275/50=55/10=5 1/2

CAN A TUTOR HELP ME WITH THIS PROBLEM PLEASE!
To understand the solution given below, you will need to know a few definitions or identities: 1. P(A)=probability of event A will happen. 2. definition of conditional probability: P(A|B)=P(A∧B)/P(B) i.e. Probability of event A happening GIVEN that B has already happened. ...

Math
Use the annuity/compound interest formula: FV=A(R^n-1)/(R-1) where A=monthly deposit R=1+interest/period=1+0.02/12 FV=future value = 20000 n=number of periods = 7*12 Solve for A, where

chemistry
Indeed, density of sand (and other soil related materials) depends on the moisture content. For dry sand, it is approximately 1.6 g/mL. Ref: http://www.rfcafe.com/references/general/density-building-materials.htm

Deposit
Use the annuity/compound interest formula. FV=Future value A=amount deposited each period = 3000 R=1+interest per period (year)=1.02 n=number years money was deposited FV=A(1+R+R^2+...+R^(n-1) =A(R^n-1)/(R-1) Take out your calculator and find FV. It should be around 150000.

Math
The five cases of congruence of triangles are: ASA SAS SSS AAS and RHS If you can find which case this belongs, then the two triangles are congruent. If not, please post again for more information.

Geometry
No problem! Yes, the best way to get more help is to post new questions, with a later time-stamp, and have more people looking at it.

Geometry
Indeed it is! The theorem applied to the present situation tells us that AD/DB = AE/EC Fill in the values of the sides (three of them) and hence calculate the remaining side before making the choice.

Chemistry
"Another method to prepare MgI2 is mixing powdered elemental iodine and magnesium metal. In order to obtain anhydrous MgI2 the reaction should be conduct in a strictly anhydrous atmosphere and dry-diethyl ether can be used as a solvent." from https://en.wikipedia.org...

MATH
A contingency table helps. Complete the table Test . has . . doesn't have result disease disease + = 0.005*0.93 0.995*.02 - = 0.005*0.07 0.995*.98 tot. 0.005 0.995 The probability of a person who tests positive actually has the disease is in one of the cells.

Chemistry
Answers to questions of this kind are usually found readily by googling the key words. For example, googling "ammonium nitrate" will give you a whole lot of information about the salt, how it's formed, the manufacturing processes, its applications/uses, etc. You ...

math
Let x=number of cars he sells. $750 is his base salary. If he sells no cars, he gets paid $750. If he sells one car, he gets paid $750+300. If he sells two cars, he gets paid $750+300×2. If he sells three cars, he gets paid $750+300×3. If he sells x cars, he gets ...

Algebraic equations real life problems
"Widths are top--3b in. bottom--(2+a)in." ⇒ 3b=2+a "Lengths are left--(3a-b) in. And right--(2+a+2b) in." ⇒ 3a-b=2+a+2b Solve for a and b, hence perimeter. Hint: both a and b are positive, and are both integers.

Business
Assuming money is deposited at the end of every month, and interest is compounded monthly, then the following annuity formula applies. FV=21000=A(1+R+R²+R³+...+Rn-1) =A(R^n-1)/(R-1) or A=FV*(R-1)/(R^n-1) where FV=future value=21000 A=monthly deposit (to be evaluated...

Math
M W M W M W M W M This means that 5 men will have 5 different places to choose from, and women will have four. Men's choices = 5*4*3*2*1 Women's choices = 4*3*2*1 They can be arranged independently, so the product of the number of choices of each gender will give the ...

Conditional Probability
See similar problem here: http://www.jiskha.com/display.cgi?id=1481848396

Math | Algebra
30% red means 70% white. Given 8 cups : 30%, then x cups : 70% Cross multiply and solve for x: x=8*70%÷30%=?

probability
Find the z-score using Z(x)=(x-μ)/σ μ=mean, σ=standard deviation. Then use the normal distribution table to find the upper tail, i.e. probability of X greater than Z(x).

Algebra
I think the problem says: f(x)=-4.7x+1 Very often checking your post before or after posting will save you time, and that of helpers. You need to know what is "domain" and "range". If you don't find the meaning of the words in your class notes or ...

math! again
3)The factors of 4 are: 1, 2, 4 The factors of 5 are: 1, 5 The factors of 6 are: 1, 2, 3, 6 Then the greatest common factor is ?.

Chemistry (Dr. Bob)
Quite right Dr.Bob. Thank you for the note. It just doesn't decompose like that. Carbon is required to reduce the oxide. Namely 2Al2O3+3C -> 4Al + 3CO2 The electrolysis part is more to help prevent the formation of CO. However, as you said, the ratio of Al and Al2O3 ...

Chemistry (PLZ HELP)
Aluminium oxide: Al2O3. Molecular mass (approx.)=27*2+3*16=102 Aluminium: Al Molecular mass=27. Write down the equation: 2Al2O3 -> 4Al + 3O2 (electrolysis) So 2 Al2O3 molecules -> 4 Al molecules. 2*102 Al2O3-> 4*27 Al 204 : 108 Use proportion to solve for the final ...

Maths
You will need to describe how the two pulleys are arranged, as well as the two blocks. Without that, it is not clear how the system is set up. You can also opt to post an image of the diagram/figure.

g.p.
This might help you to learn about a.p. and g.p.: http://www.mathcentre.ac.uk/resources/uploaded/mc-ty-apgp-2009-1.pdf

math
Y-intercept is the point where x=0. From the given function, P=(6000-400x)*(x-2) we substitute x=0 to get P=(6000-400(0))*(0-2) =6000*(-2) =-12000 It also means the loss incurred when the manufacturer gives the paper away ("selling" at a price of x=$0 per ream).

math
Use Perimeter = 2(L+W) = 20 Substitute L (that you calculated) into the equation, and solve for W, hence L.

Math
If you buy 10 apples with $2. How many apples would you get for $1?

Matrix application
"Substitute each pair of x,y values to produce 3 simultaneous equations with unknowns a, b and c" As instructed, x = 150m y = 190.650m a(150)^2+b(150)+c = 190.65 a(300)^2+b(300)+c = 611.450 a(450)^2+b(450)+c = 831.141 Form matrix, A= |150^2 150 1| |300^2 300 1| |450^...

Math
Set up equations to solve for X=number of goats in farm x, Y=number of goats in farm y. "The ratio of the number of goats in farm x to the number of goats in farm y was 9:4." => X/Y=9/4 multiply by Y to get: X=9Y/4.....................(1) "After 35 goats were...

math
Fermat's little theorem says if p is prime, and p does not divide a, then a^(p-1)≡1 mod p. Here we put p=61, therefore 61 does not divide a=8. Hence 8^(61-1)≡1 (mod 61), or 8^(60)≡1 (mod 61). Recall the multiplication rule of modulus arithmetic, 8^120&...

Math
Assuming ACD is a line segment, then by the rule of line segments, AD=AC+CD => CD=AD-AC=20-15=5 If ACD is not a line segment, then please supply additional information/description.

Algebra
R=age of Rosa A=age of Amy then form two equations using information given: "Rosa is 14 years older than her sister Amy." => R-A=14 => R=A+14.................(1) "3 years ago, she was 3 times as old as Amy." Three years ago, both were 3 years younger...

math
Let long side = S (cm) then short side = S-10 (cm) A parallelogram has opposite sides of equal length, therefore the perimeter equals 2(S + (S-10))=4S-20 We were given the perimeter is 88 cm, therefore 4S-20=88 Solve for S (the long side) and S-10 (the short side).

probability
First find out how many distinct letters are there in the word MATHEMATICS, call this number "n". For example, the word SAILING has the letters S,A,I,L,N,G, 6 out of 7 letters are distinct, while the letter I is repeated but not counted more than once. In the English...

Math
Assuming the favourite and second favourite bands are distinct (different), then there are four choices for the favourite band, and (4-1)=3 choices for the second favourite band. Use the multiplication rule to find the number of possible votes.

Math
1826.11 (1826.11019) is the correct monthly payment to obtain 100,000 at the end of four years. Note that your formula assumes that payments are made at the end of each month. The interest is the cumulative amount at the end of four years less the total amount paid, namely 4*...

Probability
Sue, You don't have to change the screen name. It will be easier for teachers to work with the same person. It would be similar to your previous question (in the name of Paige), except that to get every answer wrong, you only have three choices (and the student must know ...

Math-Probability
We will assume that all the questions are independent of each other, and that each question requires exactly one choice. That is the instruction "indicate all that apply" will not be applicable. There are four ways to arrange the answers to the first question. There ...

Stoichiometry
Yes, the limiting reactant is CaCl2. Since it is a reactant, there is no new CaCl2 formed... unless you meant something else. The same idea extends to products. The overall molecular ratios are 1:1:1:2. So you can calculate amounts of products formed using the ratio.

Stoichiometry
Na2CO3 + CaCl2 = CaCO3 + 2NaCl Yes, the first step is to write a balanced equation of the reaction. The coefficients of the balanced equation tells us the relative number of moles of each reactants is required, as well as the relative number of moles of the products. In this ...

Physics
On an inclined plane, the forces acting on an object of mass can be resolved along the incline (+ up) as follows: Gravity force+Friction force =-mgsin(θ)+Ff The above sum equals zero if the object stays in equilibrium. Therefore Ff=mg sin(&theta) The above can be derived...

Physics
Since all numbers are known for m1,m2,g and θ, we can calculate that force pulling block up-plane = T = m2g=98.1 N Force pulling block down-plane = mg sin(&theta) =58.90 N The difference is due to friction, of the amount = 39.20 N I believe you answer is correct. Book ...

Math (calculus) (mean values)
Part (a) average rate of change is the difference between the end of last month to the beginning of the first month, divided by the number of months, so Average=(s(12)-s(0))/12 Part (b) Calculate the derivative of the function s(t), with respect to t: d s(t) / dt =d(1085-1395...

Civil engineering
Hint: https://en.wikipedia.org/wiki/Varignon's_theorem_(mechanics)

Calculus
Have you read the reply: http://www.jiskha.com/display.cgi?id=1480206573 ? If you have and it was not clear to you, would you consider posting a follow-up question instead of a new post?

probability
How many of the dvrs are NOT defective? If selecting any item from the inventory has equal probability, what is the probability of selecting any NON-defective item from the 50 dvrs?

Calculus
It all depends on the size of the units. If the mean of the y-values is, say, 100, then residuals not exceeding 0.6 is ok. If the mean of the y-values is 1, then it's not acceptable. Also, it is related to the number of data, and the sign of the residuals as well. For ...

Can someone help me please I've tired this problem
See similar problem here: http://www.jiskha.com/display.cgi?id=1481848396

Data Probability
See similar problem here: http://www.jiskha.com/display.cgi?id=1481848396

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.

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: ...

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 ...

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

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 ...

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.

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.

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)...

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