Wednesday

April 1, 2015

April 1, 2015

Total # Posts: 11,138

**maths**

The idea is to convert f(x)=asin(x)+bcos(x) into the form g(x)=k*cos(a+φ) where k and φ are constants dependent on a and b. This way, it is easy to show that the max/min values of the f(x) is ±k. Start with expanding g(x) using compound angles. g(x) =k(cos(&phi...
*July 12, 2013*

**Maths**

See: http://www.jiskha.com/display.cgi?id=1373620166
*July 12, 2013*

**Math**

First find the rule of the parabola: We know that the parabola curves (is open) towards the bottom, so the rule is y(x)=b-ax² if we set the y-axis to cut the vertex. Since y(0)=16=b, so b=16 or y(x)=16-kx² Also, y(4)=0 tells us that k=1, or the rule of the doorway is...
*July 11, 2013*

**alg2 check?**

Remember that ^ has higher precedence than * or +, so in these expressions, parentheses are required: 1. (2)(3)x^(1+3) =6x^4 2. (4)^3 x^(1*3) y^(2*3) =64 x^3 y^6
*July 11, 2013*

**Math.**

Two step experiment: multiply the probability of each step. A. P(Jeans,t-shirt)=0.3*0.6=0.18 B. P(jeans, ~t-shirt)=0.3*(1-0.6)=0.12
*July 11, 2013*

**Math- important!!!**

Use binomial distribution, p=0.28, q=(1-0.28)=0.72 A) n=5 P(3/5)+P(4/5)+P(5/5) =3C5*p^3*q^2 + 4C5*p^4*q^1 + 5C5*p^5*q^0 =10(0.28^3)(0.72^2) + 5(0.28^4)(0.72) + 1(0.28^5)(0.72^0) Use your calculator to find the answer for (A) B) Expected value for binomial distribution with n=...
*July 11, 2013*

**physics**

150 * 2*3600 j + 250 * 10*60 j =1230000 j =1.23 Mj
*July 10, 2013*

**differential calculus**

Intuitively, the circle has a bigger area for the same circumference, so we try to make a bigger circle. Also, since the area increases as the square of the circumference, we want to make 1 single shape as opposed to two. So intuitive answer is to make the smallest square ...
*July 10, 2013*

**French**

Each country name has a gender and a number. The country France is feminine singular, as demonstrated by the phrase "Vive la France!" The country United States (Les États-Unis) is masculine plural. For feminine country names, we use the preposition "en&...
*July 9, 2013*

**math**

The question does not give the required context. Some countries charge sales tax on labour, and some may not. I believe Overhead rate would be added to the labour, meaning that for every $12 paid to the worker, the customer pays $12(labour)+$15(overhead)=27. If sales tax does ...
*July 9, 2013*

**Computer Programming**

Your code seems to be in reasonable shape, except that it does not yet implement the algorithm to find the maximum revenue. So the current revenue is 600*50=30,000$ a month. Your program will increase the rent by $40 steps and recalculate the revenue. When the revenue starts ...
*July 9, 2013*

**MATH:( Base systems?!**

Divide the number by the base and note the remainder on the right. The digits from bottom to top is the number required. Example: Find 37 to base 5. 37 R 2 (37/5=7 R2) 7 R 2 (7/5=1 R2) 1 So the number is 1225
*July 9, 2013*

**Number and Operations**

3,6,9 and 18, since 20/18 also has a remainder of 2.
*July 9, 2013*

**math**

The question should have read: There are 35 students in a class who stu dy either art, music or both. 15 study art. Twice as many students who study art study music. COMPLETE THE VENN DIAGRAM TO SHOW. 35 students in all 15 study art 2*15=30 study music so 35-30=5 study only ...
*July 9, 2013*

**Math 17 Synthetic Division**

Showing steps of synthetic division requires lining up many numbers vertically, which is impossible to do at this web site. I suggest you refer to examples of sites which can format number displays. Try for example: http://www.purplemath.com/modules/synthdiv.htm
*July 9, 2013*

**GEOMETRY LATERAL AND SURFACE URGENT (PLEASEHELP)**

Total surface area of a rectangular box =2(lw+wh+hl) where l,w,h=length, width and height respectively. Total surface area of a cubical box (all sides equal to "a" =6a² Total surface area of a Rectangular prism : see above for rectangular box
*July 9, 2013*

**Math**

solid: square pyramid height, h = 15 side of base, s = 5 Area of base, Ab=5^2 area of cross section at height y =Ab*(y/15)^2 Volume (using the general solid integral formula based on Simpson's rule) V=(Area at top + Area at base + 4*area at mid-height)*height/6 =(0+25+4*6....
*July 9, 2013*

**Prisms**

See: http://www.jiskha.com/display.cgi?id=1374407375
*July 9, 2013*

**Number System**

Subtraction is done as in decimal, one digit at a time from the right. Borrow from the left digit if necessary. If the result is expected to be negative, reverse the subtraction (to get a positive difference) and then change the sign. Example: 1101 -0110 ----- 0111
*July 9, 2013*

**Number System**

Not sure if the question was quoted properly, because the last group of the first number has only three digits. To add two binary numbers, we add a digit at a time just like in decimal, using the following rule: 0+0=0 0+1=1 1+0=1 1+1=0 with a carry of 1 So to add 101 to 111 we...
*July 9, 2013*

**Number System**

You can convert too hex from binary by grouping, from the right, four digits at a time: 1 1011 1011 and convert each group from binary to a decimal digit, using A for 10, B for 11...and F for 15. For example, 1011=> 8+0+2+1=11=>B so the above example becomes 1BB in hex.
*July 9, 2013*

**Computer Programming**

I suggest you give it a try and post any difficulties you encounter. Programming is not as hard as it seems once you get started.
*July 8, 2013*

**Math**

Width = x inches (given) Length = 2x inches(given) Height = 5 inches (given) Volume = 5*x*2x = 10x² in.3
*July 8, 2013*

**Math (please help me Steve)**

Here's a lower bound solution. You may want to investigate other possibilities. The number 7 can be partitioned into 3 ascending non-negative integers in 8 ways, namely: 007# 016 025 034 115# 124 133# 233# There are 3 permutations of partitions (indicated #) with non-...
*July 8, 2013*

**Math**

Both, in a minute and in an hour. The LCM of 3, 5 and 10 is the same as the LCM of 3 and 10 because 5 divides 10 (5 is a factor of 10). The LCM of 3 and 10 is 30. So the soonest the will flash together is 30 seconds.
*July 8, 2013*

**Vba**

First, the concept of sub programs is to isolate a particular calculation and make a "black box" which returns a "complicated" answer without having to worry about how it is done. On the other hand, the UI (user-interface) belongs to a separate element of ...
*July 8, 2013*

**math**

15 2's = one way 10 2's + 2 5's = 12!/(10!2!) ways 5 2's + 4 5's = 9!/(5!4!) ways 6 5's = one way Total=194
*July 7, 2013*

**Calculus**

Think of f(x)=f1(x)+f2(x) where f1(x)=x f2(x)=-cos(x) We note that f1(x) is monotonically increasing throughout [-π, π) while f2(x) is increasing between [-π, 0) and decreasing between [0,π). Therefore to find the absolute maximum and minimum, we only need to check...
*July 7, 2013*

**Statistics/Probability**

The sum P(RR)+P(PP)+P(SS)=0.3288 which rounds to 0.33.
*July 7, 2013*

**Statistics/Probability**

A is correct. I assume you know that rock wins over scissors, paper wins over rock, and scissors wins over paper. For the other parts, make a tree diagram complete with corresponding probabilities and sum all the appropriate outcomes to get the probability. Example: R=rock, P=...
*July 7, 2013*

**math**

Let x=length of one of the equal sides. Then 42=16+x+x Solve for x.
*July 7, 2013*

**Math**

Z1=(2-5.5)/3.5=-1 Z2=(9-5.5)/3.5=+1 Look up the normal distribution table to find P(Z1<Z<Z2)
*July 7, 2013*

**physics**

Wavelength = Speed/frequency Speed of light: 3*10^8 m/s Frequency = 3*10^9 Hz Wavelength = 3*10^8/(3*10^9) = 0.1 m = 10cm
*July 7, 2013*

**heeeeeelp math**

Not too sure the point of the question, but here's the answer anyway, assuming b and c are given but unknown constants. To find (max|f(x)|) for x∈[-10,10]: Complete squares to get f(x)=(x+b/2)²+c-b²/4 where (-b/2, c-b²/4) is the vertex. If -b/2 ∈...
*July 7, 2013*

**heeeeeelpm math**

Continued from http://www.jiskha.com/display.cgi?id=1373027417 Can you show an idea of your probability tree to make sure that your interpretation corresponds to what was asked? What did you get for your answer?
*July 7, 2013*

**(pls help) physics**

Q1 1kg = 1000 g It does not make sense to use a bucket of 1.5kg to pull up 10 g of water. You must mean 10 kg of water. 1.5kg+10kg=11.5 kg Work done = mgh (in consistent units) =11.5*9.8*8 j Q2 The word "average" has been used very vaguely. If it means to calculate ...
*July 7, 2013*

**physics**

Displacement = "distance" due north (requires speed and direction)
*July 7, 2013*

**physics**

Please type your post in "proper case", i.e. use lower case except for the first letter of a paragraph, sentence, or proper nouns. In posts, we use all uppercase only when we mean to SHOUT at someone. "Density bottle" is also called a specific gravity ...
*July 7, 2013*

**Math (Geometry)**

That's true, it should be the supplement of asin()=180-31.6=148 (nearest degree).
*July 7, 2013*

**Math (Geometry)**

See: http://www.jiskha.com/display.cgi?id=1373027638
*July 7, 2013*

**math**

Check: 12+12=24 3(12-4)=3*8=24 So answer is correct.
*July 7, 2013*

**math**

Make a probability tree. If the first one is white P(W)=6/10 P(WB)=(6/10)(4/9)=24/90 If the first one is black: P(B)=4/10 P(BB)=(4/10)(3/9)=12/90 P(XB)=P(WB)+P(BB)=24/90+12/90=36/90=2/5
*July 6, 2013*

**math**

The mid-point has coordinates which are the averages of those of A and B: M((-3+3)/2, (2-2)/2) or M(0,0) The length of a segment is obtained by summing the squares of the difference of coordinates, and then take square-root, namely D(AB)=sqrt((x2-x1)^2+(y2-y1)^2) =sqrt((3-(-3...
*July 6, 2013*

**Physics**

Frictional resistance = μN =μmg =μ6.2N Force required = 2.2 N Thus μ6.2 = 2.2 μ=2.2/6.2 = 0.35 approx.
*July 6, 2013*

**math - help please**

Use the definition of conditional probability: P(X9|9X) in the previous question. P(X9∩9X)/P(9X) =P(99)/P(9x) =(4/52)*(3/51) / (4/52) =3/51
*July 6, 2013*

**probability**

This is a problem of conditional probability. The shortcut to the answer is consider only the outcomes where the first child is a girl, and calculate the probability among those where both are girls. I.E. Ω={GG,GB} favourable outcome: {GG} So assuming all outcomes are ...
*July 6, 2013*

**algebra2**

Make a tree diagram assuming the products are introduced one after the other. Assuming A=success of product 1, and a=failure of product 1, etc. Required probability =P(Abc)+P(aBc)+P(abC) =(1/5)(1/3)(1/2)+(4/5)(2/3)(1/2)+(4/5)(1/3)(1/2) =13/30
*July 6, 2013*

**Math**

What is the rest of the question?
*July 5, 2013*

**math**

First factor out the common denominator of 12²=144, which then gives automatically the factorization: (3m+4n)(9m-8n)/144
*July 5, 2013*

**advanced functions**

From the function: f(x) = (x + 1)(x – 2)(x – 4)² we see that it is a quartic with leading coefficient equal to 1. So the shape of the curve is like a letter W. Since factors (x+1) and (x-2) are distinct, we see that f(x)<0 ∀ xϵ(-1,2). The double ...
*July 5, 2013*

**trigonometry**

Up 50', horizontal 200' makes an angle of elevation of atan(50/200)=14° approx.
*July 5, 2013*

**Physics**

Downward force due to gravity is F=1368.1 Friction force resisting movement is FF=1127.6 Therefore net downward force =force required to prevent load from sliding down =F-FF =1368.1-1127.6 =240.45 N
*July 5, 2013*

**Physics**

mg=4000 N is correct. θ=20° μ=0.3 (assumed static friction) Gravity force along plane F=mg sin(θ) Friction force along inclined plane =μmg cos(θ) direction acts against movement. To move load up slope: Force required =mg sin(θ)+μmg cos(&...
*July 5, 2013*

**Spanish - help required**

help required.
*July 5, 2013*

**math**

there are 360 degrees in one revolution. If it rotates at 600 rpm (revolutions per minute), then the angle it goes through in one minute is 600*360°. In one second, divide the above number by 60.
*July 5, 2013*

**Chemistry**

Each revolution moves through 360 degrees. So 48 RPM moves through 48*360° in one minute. In two seconds, the angle is 48*360*(2/60) =48*12 =576°
*July 5, 2013*

**math**

Draw a diagram and hence deduce that Height=400 sin(40°)
*July 5, 2013*

**math**

Ratio required: (54-30)/(30-26) =24/4 =6/1 Weight of 26% alloy:210*(6/7)=180 oz Weight of 54% alloy:210*(1/7)=30 oz
*July 5, 2013*

**Calculus - linearization**

Since the exact increase can be calculated readily by π(r2²-r1²) =π(44.4²-44²) =35.36π I assume you are working on linearization in calculus. Let A(r)=πr² A'(r)=2πr Approximate increase in area =A'(r)Δr =2πr*Δr =2&...
*July 5, 2013*

**heeeeeeeelp math**

Given ΔABC, A=20° B=80° => C=80° => isosceles triangle with base BC=x. Let E=mid-point of BC, then ΔAEC is a right triangle right-angled at E EC=x/2 By definition of cosine, AC=(x/2)/cos(80°) =x/(2cos(80°)) Consider ΔADC, AD=x (given...
*July 5, 2013*

**heeeeeeeeeeelp math**

The way I interpreted the question is that she does not move at all if she rolls doubles. After rereading, it looks like that when she rolls doubles, she moves the token before rolling again, and on the third double, she advances it to 36. If this latter interpretation is ...
*July 5, 2013*

**heeeeeeeeeeelp math**

Solve using a probability tree. First calculate the outcomes with distinct rolls for a sum of P(x)=30/36. For simplicity, the probability is multiplied by 36 to use integers. sum=x 36*P(x) x*36*P(x) 3 2 6 4 2 8 5 4 20 6 4 24 7 6 42 8 4 32 9 4 36 10 2 20 11 2 22 Sums of 2 and ...
*July 5, 2013*

**Math**

One kilogram is equivalent to 1000 grams. So 4.86932 kg = 4.86932*1000 g = 4869.32 g To round to the nearest gram, we draw a vertical line at the decimal point: 4869 | 32 if the first digit after the | bar is 5 or over, we add one to the number before the bar. Otherwise we do ...
*July 5, 2013*

**Physics**

There is probably a typo: ...east at 4.0m/s for 0 seconds. should probably read ...east at 4.0m/s for 30 seconds. Sum up all the individual displacements to get the overall displacement. Let +x=east, +y=north, then (dx,dy) =(-2*15+0+4*30, 0+3*20+0) =(90, 60) =108.17 in ...
*July 4, 2013*

**Math Calculus**

The domain of the function is all Real, except for those two points which will result in a zero in the denominator, and hence f(x) will not be defined. One of these points is x=7. The roots can be deduced from the numerator of f(x). One of the roots is x+1=0, or x=-1. Vertical...
*July 4, 2013*

**C++ debugging**

If you need to debug a programme, it would help more if you specify: 1. object of the programme 2. language (C++ in this case) 3. What does not work: - does not compile? (error message?) - does not run ? (error message?) - does not give proper answer (logical error) - loops ...
*July 4, 2013*

**math 3**

Add three times the second equation to the first to get: (10+15)x=-16+66 25x = 50 x=2 Substitute x=2 into the second equation to get: 5(2)+2y=22 2y=22-10=12 y=6 Now substitute x=2 and y=6 into the first equation to check solution 10(2)-6(6)=-16 so solution is correct.
*July 4, 2013*

**math**

As Reiny pointed out, we do not use tables for the past 40 years, so we can only guess what's shown in the tables. My guess would be that the factor is the ratio of future/present values, namely: 1.005^48=1.270489 Note: compound interest is calculated as: future value=...
*July 3, 2013*

**Statistics**

Your reasoning and calculations are correct. So the probability of getting a prime number as the sum is 15/36.
*July 2, 2013*

**Stats**

An even number is any of 2,4,6,8,10,and 12 (within the sample space above). So the probability of throwing a sum equal to an even number is the sum of the corresponding probabilities, namely: 1/36+3/36+5/36+...1/36.
*July 2, 2013*

**math**

By trial and error, I get: 11^3+(-5)^3+(-6)^3=990 If we assume the largest integer is N such that N(a,b)=a^3-b^3-(a-b)^3 =3ab(a-b) The likely candidates are: 990=3*11*5(11-5)... a,b,c = 11, -5, -6 993=3*331 996=3*332=3(4*83) 999=3*333=3(9*37) All of which cannot be reduced to ...
*July 2, 2013*

**probability**

The experimental probability of multiple births is #of multiple births/total # of births =(68339+1337)/3612258 =1.9% (approx.) Check my arithmetic.
*July 2, 2013*

**compound interest math**

calculate the compound interest on an investment of $45,000 at 6% interest compounded quarterly fro 3 years Formula for compound interest: A=P(1+i)^n A=amount at the end of n periods (future value) P=amount invested (present value) i=interest per compounding period. 6% per ...
*July 1, 2013*

**Math**

Check for type, I believe the question should read: (8/(sqrt(x)-3)) - (48)/x-9) =(8(sqrt(x)+3)/(x-9)- 48/(x-9) ... multiply top & bottom by sqrt(x)+3 =(8sqrt(x)-24)/(x-9) =(8(1/2)/sqrt(x)) / 1 ... diff. top and bottom, de l'hôpital's rule =4/3
*June 25, 2013*

**math**

4x4x4x4 =4^4 =(2^2)^4 =2^(2*4) =2^8
*June 25, 2013*

**Discreet math**

If you need a proof of the proposition/identity, please first double check the expressions. [(pvq)^(p=>)^(q=>)]=>r[(pvq)^(p=>)^(q=>)]=>r Not sure if something is missing where expression is indicated in bold. Perhaps there are other problems.
*June 25, 2013*

**Math :)**

You're welcome!
*June 25, 2013*

**Math**

Typo corrections: Area of square PRSQ - Area of ΔPDQ - area of sector RPD - Area of sector SQD. Note that sectors RPD and SQD have central angles of (90-60)=30°.
*June 25, 2013*

**Math**

We will describe the problem as follows. Two circles A,B of equal radii (r=30') are centred at P, Q, distance r apart. Points R and S on circles A, B are such that RS form a common tangent to both circles. Hence PRSQ form a square of side r. Arcs are drawn with centre P ...
*June 25, 2013*

**devry**

Divide total cost by the number of miles driven to get the average cost per mile, $773.02 / 180 miles = ? $/mile
*June 24, 2013*

**Physics (Stress & Strain)**

Area = lw (correct) =1cm x 2.5 cm =0.0100 cm x 0.025 cm =0.00025 m² (remember, length 8.1 does not come into the calculation of cross section area) Stress =force (in N)/area (in m²) =150000/0.00025 Pa =6×10^8 Pa =6×10^5 mPa =600,000 mPa Strain =...
*June 24, 2013*

**Algebraic Fractions**

6x/(12x) would be simplified just like an ordinary (numeric fraction). Look for common factors in the numerator and denominator to cancel out, separately for numeric values and variables. For the numeric part, the HCF is 6 and for variables, it is x. So divide both numerator ...
*June 24, 2013*

**Physics (Stress & Strain)**

Correct!
*June 24, 2013*

**Physics (Stress & Strain)**

Stress = force / area Load is 87500N which is just a force. You need to divide the force by the area resisting the tensile stress. Factor of safety is then ultimate stress / stress under load
*June 24, 2013*

**Physics (Stress & Strain)**

Do not forget to multiply by 10^-4 when converting cm² to m² Here we are talking about shear stress, which is dependent on the thickness and the circumference of the hole, not the area. Surface area which resists shear force is similar to the lateral surface area of ...
*June 24, 2013*

**math - please check question**

There must be a typo, because the cheapest ticket is $7, which when multiplied by 1275 gives 8925, much higher than the revenue of $2490. Assuming total of 275 tickets sold. x=number of adult tickets 275-x=number of children's tickets Then 12x+7(275-x)=2490 Solve for x to ...
*June 24, 2013*

**Physics**

So is it 30 m/s or 35 m/s? Let the initial velocity be u m/s, which remains constant while it is airborne. Time to drop down 1.5 m vertically with g=9.81 m/s^2 is given by S=(1/2)gt^2 or t=√(2S/g)=√(2*1.5/9.81)=0.553 s Horizontal distance covered before touching ...
*June 24, 2013*

**Math 61 part 2**

To solve this category of problems where you need the area/centroid of a region bounded by two curves, you need to first find TWO intersection points of the two curves by equating y1(x)=x^2 and y2(x)=2*x+3. The intersection points are at x=-1 and x=3, with y2(x) above y1(x). ...
*June 24, 2013*

**How do I solve for this??**

H (joules) =ΔT*m*Q where H=energy required (joules) ΔT=change in temperature (°C) m=mass (g) Q=specific heat in j/°C/g So heat gain =12.67 °C * 100 g * 4.180 j/°C/g =5296 j
*June 24, 2013*

**physics**

non-zero and constant.
*June 24, 2013*

**math**

Find the slope of the line that joins (0,-1) and the centroid of the parallelogram which is (8.5,4), or the mean of all the coordinates.
*June 24, 2013*

**Physics**

See: http://www.jiskha.com/display.cgi?id=1372082354
*June 24, 2013*

**Physics**

See: http://www.jiskha.com/display.cgi?id=1372082354
*June 24, 2013*

**Math**

Since 31^2=961<1000, and 32^2=1024>1000 we can have a maximum of 31 pairs of numbers whose product would be less than 1000. So the maximum number of runners would be 62.
*June 23, 2013*

**Physics (Stress & Strain)**

When you see a factor of safety over 10, it would be a good idea to check your calculations. Watch out for units conversions for areas and volumes. In converting 6.5 cm² to m², you must multiply by the (linear factor)², namely 0.01². The area is therefore 6...
*June 23, 2013*

**Physic (Stress & Strain)**

Both are numerically correct. In #2, you divide m by m, hence no units.
*June 23, 2013*

**math**

This is similar to a previous question. I believe it would do you good to plot the scatter diagram and calculate the regression line according to the formula. Post again if you have difficulties. For your information, the regression coefficient a is between 0 and 0.2, the ...
*June 23, 2013*

**statistics check :)**

You're welcome!
*June 23, 2013*

**statistics check**

I got it from summing (y-yBar)^2, and I had yBar=24.3.
*June 23, 2013*

**statistics check**

SE² is given by: [ Σ(y-yBar)^2 - [Σ(x-xBar)(y-yBar)]²/Σ(x-xBar)² ] /(n-2) I get: Σ(y-yBar)²=258.1 Σ(x-xBar)(y-yBar) = -168.7 Σ(x-xBar)²=296.9 n=10 to get se²=20.28
*June 23, 2013*

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