Thursday

June 30, 2016
Total # Posts: 41,524

**value**

planes fly on headings, not bearings. Use the law of cosines: CA^2 = AB^2 + BC^2 - 2*AB*BC*cos(41+50)° You can easily get AB and BC using distance = speed * time.
*June 25, 2016*

**math**

finite: 1,5 infinite: 2,3,4
*June 25, 2016*

**ALGEBRA**

since time = distance/speed, if the man's walking speed was w, then we have 180/12w - 3 = 6/w w = 3 so, he drove at 36 mi/hr, doing the 180 miles in 5 hours.
*June 25, 2016*

**algebra**

http://www.jiskha.com/display.cgi?id=1466735810
*June 25, 2016*

**English**

#1 and #2 are the same #3 and #4 are the same, but stronger than 1 & 2.
*June 25, 2016*

**Math**

sin37° is very close to 0.6, so cut 'em some slack. The 6-8-10 triangle has one angle of 36.87° I assume they want other trig functions using that triangle.
*June 25, 2016*

**science**

volume = mass/density
*June 25, 2016*

**science**

density = mass/volume = 1.75g/2.5cm^3
*June 25, 2016*

**science**

Beneath the surface, gravity is basically a linear function of the radius. So, at 1/100 the radius, g is reduced by a factor of 1/100 See the discussion here: http://physics.stackexchange.com/questions/99117/why-gravity-decreases-as-we-go-down-into-the-earth
*June 25, 2016*

**math**

If C was in the business for x months, then the weighted investment is (20000*12 + 40000*9 + 100000x) * x/12 = 55000 x ≈ 1, so C joined after about 11 months
*June 25, 2016*

**geometry**

why post such questions that can be simply evaluated on any decent calculator? Or by google? If you mean tan^-1(9) then that is 83.65° sin^-1(0.62) = 38.32°
*June 25, 2016*

**geometry**

no idea. Where the heck is U?
*June 24, 2016*

**Mathematics**

cc = 0
*June 24, 2016*

**Math HELPPPPP**

(a) x/7 + y/11 = 1 y/11 = -1/7 x + 1 y = -11/7 x + 1 The answer is -11/7, not -11/7 x (b) You have a point and a slope, so use the point-slope form! y-3 = -5/3 (x-2) Now just rearrange that into slope-intercept form as needed.
*June 24, 2016*

**algebra**

well, you know that y = vt - 4.9t^2 max height is at t = v/9.8
*June 24, 2016*

**physics 1**

x = 2t^3 v = 6t a = 6 To find an average, just divide the change by the interval. (a) x(1) = 2 x(2) = 16 avg v = ∆x/∆t = (16-2)m/(2-1)s = 14m/s I think you can handle the rest, no?
*June 24, 2016*

**CHEMISTRY - My Bad**

yeah - sorry. I read some of your other posts and saw what was going on.
*June 24, 2016*

**CHEMISTRY**

You must keep the ions in their proper proportions. NO3 is the ion, so changing it to NO6 is bogus. Maybe you should try (NO3)2 Or, if NO is the ion, then (NO)3 would give you three of them.
*June 24, 2016*

**CHEMISTRY**

not unexpected, since there is no Carbon present. Did you try Nitrite? Carbonate is CO3
*June 24, 2016*

**Math**

just add 3 to x and 6 to y in each coordinate pair
*June 24, 2016*

**math**

Assuming that Tn = ar^n that means that T1 = a Tn+1 = Tn * r
*June 24, 2016*

**math**

the hectares answer is way off. Each mi^2 is 259 hectares The gas savings is 33.33-25 = 8.33 so each of you would save $4.16
*June 24, 2016*

**Math (pre-celc 12)**

Nope. You didn't do what I told you. (f+g)-(f-g) = 2g so, 2g = (10-3x)-(5x-14) 2g = 24-8x g = 12-4x Now just check to be sure that your answers work: f+g = (x-2)+(12-4x) = 10-3x now check f-g the same way
*June 24, 2016*

**math**

a = (√3-√2)/(√3+√2) b = (√3+√2)/(√3-√2) Clearly ab=1 Doing the squares directly is a bit cumbersome, so let's rationalize the denominators: a = (√3-√2)^2 = 5-2√6 b = (√3+√2)^2 = 5+2√6 Now ...
*June 24, 2016*

**Math**

clearly, real-world distances cannot be negative. You have to use a little common sense along with the math. Even if you allowed for negative distance, that would mean the boat burrowed into the cliff!
*June 24, 2016*

**science**

Nope. p = mv 0.5 = 50v 0.01 = v v = 0.01 m/s Try redoing your calculation and you will see that the units do not wind up as m/s.
*June 24, 2016*

**Math**

w+y = 30 9.95w + 13.50y = 351.75 Now just solve for w and y
*June 24, 2016*

**math**

500 e^(7*.04)
*June 24, 2016*

**math**

Note that if x = 5-2√6 1/x = 5+2√6 Now just crank it out
*June 24, 2016*

**math**

just plug and chug: #(#3) = #(3^2-3) = #6 = 6^2-6 = 30
*June 24, 2016*

**maths**

multiply top and bottom by 5-√3: (5-√3)/(5+√3) = (5-√3)^2/22 now just expand that out to see a and b.
*June 24, 2016*

**SIMULTANEOUS EQUATION**

5x^2-5x-63 = 5(x^2-x) - 63 Recall that (x-a)^2 = a^2-2a+a^2 Here we have 2a = 1, so a = 1/2. So, add and subtract 1/4 * 5 = 5(x^2-x + 1/4) - 63 - 5/4 = 5(x - 1/2)^2 - 267/4 To get the roots, set that to zero: 5(x - 1/2)^2 - 257/4 = 0 5(x - 1/2)^2 = 257/4 (x - 1/2)^2 = 257/20 x...
*June 24, 2016*

**Simultaneous equation**

From the first equation, x = (3y+14)/5 Use that in the other equation to get 3(3y+14)/5 + 5y = 18 9y+42 + 25y = 90 34y = 48 y = 48/34 = 24/17 = 1 7/17 x = (3y+14/5) = (72/17 + 14)/5 = 310/85 = 3 55/85 = 3 11/17 You could also have used other substitutions for x, or using the ...
*June 24, 2016*

**maths**

The first digit cannot be zero, so it must be 1,2,3,4 Now just start listing them: 103 112 ... 310 400
*June 24, 2016*

**math**

you need to remember that you can always multiply by 1 without changing anything. The trick is to make sure that the units cancel correctly 1 ton = 2000lb that means that 1ton/2000lb = 2000lb/1ton = 1 8.9*10^5ton * 2000lb/ton * 1kg/2.204lb = 8076*10^5kg or, 8.076*10^8kg or,you...
*June 24, 2016*

**math**

1st two are ok 2.9x10^11 = 0.029x10^13 Now you can add them to get 3.729 x 10^13
*June 24, 2016*

**Pre-Cal**

each inverse trig function has a principal domain. Review those. tan 5π/6 = -tan π/6 = -1/√3 but, tan^-1(-1/√3) = -π/6 cos -π/4 = cos π/4 = 1/√2 but, cos^-1(1/√2) = π/4
*June 24, 2016*

**Math**

or, you are reducing the concentration by a factor of 4/10, so you must increase the volume by a factor of 10/4. 10/4 * 40 = 100 So, you must wind up with 100ml, by adding 60ml of water.
*June 24, 2016*

**Math year 10**

since s=k-5, the product is ks = k(k-5) or s(s+5)
*June 24, 2016*

**Math**

4/80 = 5% of the caught fish were tagged. So, the 70 tagged fish must be about 5% of the total population.
*June 23, 2016*

**algebra**

f(1.5) = -4.96 f(1.8) = +0.77 Since f is continuous on the interval, and 0 is between -4.96 and +0.77, f must be zero somewhere in that interval. It cannot change from negative to positive without going through zero.
*June 23, 2016*

**Physics**

find v, the speed of sound. If the depth of the well is y, then the time taken for the sound to come back is y/v Using the equation of motion, we have 4.9t^2 = y Thus, the time it takes to hit the water is √(y/4.9) Adding up the times, we have √(y/4.9) + y/v = 0.6 ...
*June 23, 2016*

**Pre-Cal: Word Problem**

can you see how unhelpful that response is? What did you enter, and why was it wrong?
*June 23, 2016*

**Pre-Cal: Word Problem**

on the interval [-90,90] sin^-1 is 1:1 For cos^-1, the domain is [0,180] But you probably want radians instead.
*June 23, 2016*

**Math**

(a) using shells, v = ∫[1,3] 2πrh dx where r = x+2 and h=y=ln(x) using discs, v = ∫[0,ln3] π(R^2-r^2) dy where R=5 and r=x+2=2+e^y (b) use the same ideas with a horizontal axis. Just keep in mind the volume of a disc (or a washer with a hole inside) and a...
*June 23, 2016*

**maths**

100u+10t+h = 100h+10t+u - 396 u-t = t-h solve that and you get t = h-2 u = h-4 h = t+2 = u+4 since no digit is zero, we can have 531 642 753 864 975
*June 23, 2016*

**math**

18f = 33g f/g = 33/18 = 11/6
*June 23, 2016*

**Physics**

Hmmm. your math looks good. Using the 5.8R and 19.6 I get (2)(3.14)(5.8)(6.4 * 10^6)(1.22) = 284,398,592 which agrees with their rounded answer for distance. Divide that by 86400 seconds and it gives a speed of 3291 m/s, which is pretty close. Is your answer anywhere near ...
*June 23, 2016*

**Physics**

figure the radius R of the orbit The distance traveled in one orbit is thus 2πR Now just figure how many orbits it makes in 24 hours. That will give the total distance traveled. Then just divide that by the time (86400 s) to get the speed.
*June 23, 2016*

**Calculus**

(a) The semicircles have a diameter equal to x, or y/5. So, each semicircle has an area of πd^2/2 = π/2 (y/5)^2 = πy^2/50 Now add up all the thin discs and you get a volume of ∫[0,10] π/50 y^2 dy = 20π/3 (b) Now the sections have diameter equal ...
*June 23, 2016*

**Math(Please Help Assignment Due Tomorrow)**

you can get a handle on this stuff at http://davidmlane.com/hyperstat/z_table.html
*June 23, 2016*

**Math (pre-celc 12)**

or, now that you know f, f+g-f = g so, g(x) = (10-3x)-(x-2) = 12-4x
*June 23, 2016*

**Math (pre-celc 12)**

come on; this is Algebra I (f+g)-(f-g) = 2g 2g = (10-3x)-(5x-14) = -8x+24 g(x) = -4x+12
*June 23, 2016*

**Math (pre-celc 12)**

(f+g)+(f-g) = 2f so, 2f(x) = (10-3x)+(5x-14) = 2x-4 f(x) = x-2 You can find g(x) in a similar way.
*June 23, 2016*

**for all real numbers x and y,it x*y=x(x-y) then x***

Let z = x*y = x(x-y) x*(x*y) = x*z = x(x-z) = x(x-(x(x-y)))
*June 23, 2016*

**Math**

If the height is h miles, then h cot3.5° - h cot9° = 13
*June 23, 2016*

**math**

extra parentheses are often useful when entering expressions online, as formatting is often rudimentary The text formatting in printed material often makes the parentheses unnecessary In any case, if the expression is unambiguous without the parentheses, they are unnecessary.
*June 23, 2016*

**Math**

There is no such number. Now, if you mean integers, then that would be 6499 or 6500 depending on your rules for rounding with terminal 5's. And next time ask a question, instead of just dropping a misspelled sentence fragment with bad grammar.
*June 23, 2016*

**Chemistry**

so, you have 75 grams How many moles of bentoite is that? Note that each mole of bentoite contains 3 moles of Si.
*June 23, 2016*

**Psychological Stats**

you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*June 23, 2016*

**MATH**

10^-4 million = 10^-4 * 10^6 = 100
*June 23, 2016*

**math**

#1 because (x-y)^2 = (y-x)^2 why don't you try the others? Just remember that (z)^2 = (-z)^2
*June 23, 2016*

**maths**

xy = 5/6 x/y = 15/8 6xy = 5 8x/15 = y 6x(8x/15) = 5 48x^2 = 75 x^2 = 75/48 = 25/16 x = 5/4 y = 2/3
*June 23, 2016*

**Algebra**

If there are w,x,y,z pizzas of the sizes, then we have 100w+144x+196y+256z = 300*256 z >= 150 y > x 40 <= w <= 50 You have said nothing about how much they need to make from the sales, so the price information is just noise.
*June 23, 2016*

**Calculus**

for a cube of side s, v = s^3 dv/dt = 3s^2 ds/dt Thus, ds/dt = 2/15 mm/s a = 6s^2 so da/dt = 12s ds/dt da/dt = 16 mm^2/s
*June 23, 2016*

**Algebra**

assuming simple interest, 2500*7*r/12 = 19.76 r = .0135, or 1.35%
*June 23, 2016*

**Algebra**

Jack bought x/3 - 10
*June 22, 2016*

**Algerbra**

There are none. All accounted for by the equation.
*June 22, 2016*

**Math**

7, since there are 7 apples. I suspect you have omitted something.
*June 22, 2016*

**Math (exam tomorrow)**

In that case, just look at the graph. It is clear that cos(x) is steepest where it crosses the x-axis. Without calculus, I can't think of an analytical test to prove where the slope is steepest. Are there any similar problems in your text?
*June 22, 2016*

**Math (exam tomorrow)**

the slope is given by the derivative f(x) is increasing fastest where the slope is steepest. That is, the derivative has a maximum. Take a look at the graphs of f and f' and you will see that for this problem, f is increasing fastest when x = 3π/4 http://www....
*June 22, 2016*

**math**

No way to tell. All we know is that wxy is isosceles, and wx < 38
*June 22, 2016*

**Math**

What you have is 4 d^4 w^3 * 6 d w^4 ---------------------------- 3 d^3 w * 8 d w^2 collecting powers of each variable, that is 24 d^5 w^7 ----------------- 24 d^4 w^3 I think you can see what cancels out now, right?
*June 22, 2016*

**math**

If you mean 4(2^(x^2)) = 8^x 2^2 * 2^(x^2) = (2^3)^x 2^(2+x^2) = 2^(3x) 2+x^2 = 3x I'm sure you can do that. Next time you post one of these, try showing some of your work first, ok?
*June 22, 2016*

**Maths**

I can't parse your words. Try using math symbols instead. Something like x((3 * 1/5)+(3 * 1/10)) = 9/10 or something. You've mangled the values and operators.
*June 22, 2016*

**math**

If the base has side x, then x^2 + 4x(x+1) = 96
*June 22, 2016*

**math**

NO, YOU DO NOT When you divide 345 by 145 you get 2.3 You are doing it backwards! By hand, you need to start out with 345)125 345 is the divisor, not the dividend!
*June 22, 2016*

**math**

you are dividing backwards: 345/145 = 2.3
*June 22, 2016*

**Math**

To figure the height after 1 minute, h/150 = tan 28°29' Now, having h, you know that 3h is the altitude after 3 minutes. So, find the angle θ such that tanθ = 3h/150 Or, in one step, θ = arctan(3*150*tan28°29')
*June 22, 2016*

**MATH ARITHMETIC SEQUENCES**

I assume you meant 1,1.1,1.2,... Tn = 0.9 + 0.1n So, to find which term is 3, 0.9 + 0.1n = 3 0.1n = 2.1 n = 21 So, T21 = 3 Makes sense. Every 10 terms another 1.0 is added: T1 = 1 T11 = 2 T21 = 3 T31 = 4 ...
*June 22, 2016*

**Science**

google is your friend. Just type in the left side of the equation and you will get many hits showing the balanced result.
*June 22, 2016*

**Math**

If the 100 is in base 2 or 5, then 100*100*100 = 1000000 regardless of base
*June 22, 2016*

**maths**

just add 180°
*June 22, 2016*

**math**

If we're allowing decimals, then I'd say the smallest is 0.123456789 If not, then I'd have to go with 1,023,456,789
*June 22, 2016*

**math**

Since 13.5 = 3*4.5, 3 times as much zinc is also used.
*June 22, 2016*

**math**

since 8 = 2^3, you have 2^2 * 2^x = 2^(3x) 2^(2+x) = 2^(3x) 2+x = 3x x = 1 check: 4(2^1) = 8^1 4*2 = 8 yep
*June 22, 2016*

**math**

just type your rational function in at wolframalpha.com Be sure to use parentheses. It will show how it interprets your input.
*June 22, 2016*

**maths**

suppose that there is a number x such that 0/0 = x Now, clearing the denominator, we have 0 = 0*x but that is true for any x, so 0/0 is undefined.
*June 21, 2016*

**Math**

or, if you really do want grams, figure how many grams of dextrose are in 100ml of the solution
*June 21, 2016*

**geometry**

I think you left out some coordinates. However, E is clearly 1/4 of the way from C to D.
*June 21, 2016*

**CALC**

dy/dx=−4xe^(y−x^2) dy/dx = -4xe^y e^(-x^2) -e^-y dy = 4x e^(-x^2) e^-y = c-2e^(-x^2) y = -ln(c - 2e^(-x^2)) since y(1) = 11, -ln(c-2e^-1) = 11 c - 2e^-1 = e^-11 c = 2e^-1 + e^-11
*June 21, 2016*

**math**

add up all the fares and divide by how many days.
*June 21, 2016*

**Math/Conversions**

Your answer is how much was left, not how much she drank. Read the question carefully...
*June 21, 2016*

**Algebra**

x/5 - g = a x/5 = a+g x = 5(a+g)
*June 21, 2016*

**PHYSICS**

F=ma the tension in the string is the downward weight of the 2kg mass. The force on the 3kg mass is that weight.
*June 21, 2016*

**math**

Draw a diagram. If the chord has length 2x, then x/200 = sin 34°
*June 21, 2016*

**maths**

That would be 8(1+2+3+...+14+15) You can find the sum of the first n numbers, right?
*June 21, 2016*

**maths**

using the law of cosines, AC^2 = 96^2 + 80^2 - 2*96*80 cos56°
*June 21, 2016*

**math**

3/8
*June 21, 2016*