# Posts by Scott

Total # Posts: 3,148

**Trigonometry**

Pythagoras ... x^2 + 35^2 = 37^2

**Trigonometry**

the diagonals bisect each other use the law of cosines to find the sides

**science**

the molar mass of HCl is ... 36.46 g

**Mathematics**

pyramid ... v = 1/3 (base area)(height) ... v = 1/3 * (2s)^2 * s = 4/3 s^3 prism ... v = l w h = 2s * 2s * s = 4 s^3

**chemistry**

the speed of sound in air is temperature dependent 337.5 m/s 10ºC

**physics**

the "beats" are the frequency differences a) 440 Hz ± (12/2) Hz b) 435 Hz ± (33/3) Hz which frequency is in both possibilities?

**Math**

6 min is correct ... but it is after 5:00 - not before

**Math (Algebra)**

if you subtract the equations (to eliminate y), you still end up with ... 0 = x^2 - x - 2 ... but you have used elimination even with elimination, you have to substitute back at some point to find all the variables

**Math (Algebra)**

x^2 = x + 2 x^2 - x - 2 = 0 (x - 2)(x + 1) = 0 x - 2 = 0 ... x = 2 x + 1 = 0 ... x = -1 the line intersects the parabola in two places plug the x-values into the equations to find the corresponding y-values

**physics**

time up equals time down ... Tu = Td half of the flight time (Tu) is spent climbing to the max ... h = 1/2 g (Tu)^2 the vertical velocity equals ... g Tu initial velocity is the vector sum of the vertical and horizontal ... V^2 = (Vh)^2 + (Vv)^2

**Physics**

Ff = ? m g cos(30º)

**Honors Algebra**

450 = 100 e^(kt) 4.5 = e^(6k) ln(4.5) = 6 k k = [ln(4.5)] / 6

**physics**

use the average speed on an interval, multiplied by the time of the interval add the three intervals

**Physics**

the two players experience equal but opposite impulses from the collision M1 * A1 = M2 * A2

**MATH**

half of the letters are vowels so, one half times one half

**Math Check! #3**

8C4 = 70

**Math Check!**

yes

**physics**

looks good

**Physics**

the force component of the box's weight along the ramp is ... m g sin(30º) the frictional force is ... ? m g cos(30º)

**math**

1st ... 1/4 * 7/16 2nd ... 1/4 * 7/15

**Math**

it's binary ... correct or incorrect P(correct) = 1/4 ... P(incorrect) = 3/4 (c + i)^50 .25^50 + 50 .25^49 .75^1 + 1225 .25^48 .75^2 ... + 1225 .25^2 .75^48 + 50 .25 .75^49 + .75^50 this is the expected outcomes for a simulation you could roll a 4-sided die (tetrahedron) ...

**Statistic**

I would agree

**physics**

30 km/s in a car!?!? that's about 3 times escape velocity

**Math**

10 - .13 < w < 10 + .13

**Physics**

a mole of gas occupies 22.4 L at 0ºC and 1 atm moles = (4.5/22.4)(273/350)(22/101) molecules = moles * Avogadro's number

**Algebra**

3 (b - c) = b + c 3b - 3c = b + c ... 2b = 4c

**Geometry**

the slant part of the cone (lateral area) is a sector of a circle the radius of the circle is the slant height of the cone ... Hs^2 = 62^2 + 12^2 the partial-circumference of the sector is the circumference of the base of the cone ... 24 ? LA = ? * Hs * 12 = 2381 base area...

**math**

the x-coordinate is constant, but the y-coordinate changes what does the slope equation (m = ?) tell you?

**Math**

the outside diameter is 8 ft more than the inside ? times 8 ft is about 25 ft 802 is WAY high

**precal**

it takes a second for the coin to reach max height, 16 ft above the balcony d = 1/2 a t^2 346 - 90 = 1/2 g t^2 solve for t, add in the 1st second

**Math**

50 cm * ? * 25

**Physics**

the deceleration is ... (13.0 -10.9) m/s / 2.20 s ... slightly less than 1 m/s^2 so it takes about 13 s to stop ... during which the average speed is ... (13.0 + 0) m/s / 2

**Science**

f = m a ... w = m g ... m = w / g

**Physics**

1/2 m v^2 = m g h h = v^2 / (2 g)

**algebra**

the question asks about "carriers" (like the RL parent) what percent is like the RL parent?

**math**

2 equations and 2 unknowns, just solve the system by substitution or elimination

**math**

looks good

**algebra**

the distance is the hypotenuse of the right triangle ... use Pythagoras

**Algebra**

the max A lies on the axis of symmetry Wmax = -b / 2a = -200 / (2 * -2) = 50

**calculus**

the quadratic solutions are relative max/min points on the graph (you obviously want the max) test the solutions in the original equation x < 4 because of the 8 in side

**maths**

the reflection is along a line through the center of the circle, perpendicular to the given line slope of perpendicular is ... -1 equation of perpendicular ... y-3 = -1 (x-2) ... y = -x + 5 intersection with reflecting line ... (1,4) center of reflected circle ... (0,5) center...

**Math**

subtract 8 ... -m/5 > 2 multiply 5 ... -m > 10 divide -1 ... m < -10

**Gr 12 Data**

a) 2^5 c) 2^3 ... arrangements of 3 middle coins d) 2^2 ... arrangements of 2 end coins e) yes , a coin toss is a coin toss

**science**

the masses are inversely proportional to the heights ... higher height means lower mass Hb Mb = Hj Mj

**geometry**

the general equation is ... (x - h)^2 + (y - k)^2 = r^2 r is the radius , (h,k) is the center

**Statistics**

25 people bought 35 cones so 10 people bought both 5 only van - 10 both - 10 only choc

**geometry**

(x - h)^2 + (y - k)^2 = r^2 the equation defines a circle of radius, r; centered at (h,k)

**math**

? rs = 20 b ... 1.1 ? rs = 22 b ? rs = 22 (b - .25) + .20 = 22 b - 5.3 .1 ? rs = 5.3 ? = 53

**Maths**

adding 5 ... | x | > 11 x < -11 , x > 11

**Math**

looks like #5

**Math**

how many are what age?

**math**

it's a 5-12-13 Pythagorean triple

**Math**

remember the hierarchy of operations ... PEMDAS adding 5 ... c/4 = 9 multiplying by 4 ... c = 36

**word problem**

Ar + Au + D + B = 267 Ar = Au - 8 D = 2 Au B = 5 Au + 5 substitute in the 1st equation to find Au ... then substitute back to find the others

**Math**

looks good

**Physics 20**

p1 exerts the same force on p2 that p2 exerts on p1 f = m a ... m1 a1 = m2 a2

**Science**

rethink #2

**algebra**

subtracting 5 shifts the 1st function 5 units down to give the 2nd function

**binomial distribution**

(s + f)^5 s^5 + 5 s^4 f + 10 s^3 f^2 + ... 10 s^2 f^3 + 5 s f^4 + f^5 s = p(success) = .687 f = p(failure) = 1 - p(success) = .313

**Math**

the terms are getting larger ... diverging

**graphing help?**

there is a website called fooplot you should use it

**Bio chem**

How many mL of 0.80 molar NaOH must be added to 20 ml of 0.40 of molar propionic acid, in order to produce a solution with a pH of 4.89? (PKa of propionic acid is 4.89.)

**consumer math**

2000 (1 + .08)^6

**math**

85000 + [(39637 - 35416) / .45]

**Physics**

boat components ... W ... 25 cos(35º) = 20 ... N ... 25 sin(35º) = 14 add the boat components to the current (14 N + 18 S) + 20 W = 20 ... the tan of the angle is ... S/W ... arctan(4/20) = 11º ... [W11ºS]

**Math**

the trip times are not the same, so the average speed is not 9 mph sorry, Ms. Sue

**Math**

d = r t ... t = d / r 27/60 = (d / 10) + (d / 8) 54/120 = (12 d / 120) + (15 d / 120) d is the distance to the lake

**Math**

get all the equations into slope-intercept form (y = mx + b) 1. the slopes are the same but the intercepts are different ... the lines are parallel ... they never intersect so no solution 2. the slopes are the same and so are the intercepts ... the lines lie on top of each ...

**Math, Algebra**

(2s + 5)(s - 6) = s^2 2s^2 - 7s - 30 = s^2 s^2 - 7s - 30 = 0 (s - 10)(s + 3) = 0

**trig**

Upper? plane ... N component ... 450 kph cos(45º) ... E component ... 450 kph sin(45º) wind ... N component ... 60 kph cos(30º) ... W component ... 60 kph sin(30º) add the components to find the resultant vector

**math**

it's four times as tall in the picture, so it's four times as tall in real life

**Math**

p + g = 20 4p + 2g = 70 solve the system using substitution or elimination

**7th grade math**

10 ft long and 4 ft wide is 40 ft^2

**Algebra**

4 w + 2 k = 62 w + k = 21 solve using substitution ... or elimination

**physics**

centripetal force is ... m v^2 / r a) (2 ? r) / 6.10 m/s b) m [g - (v^2 / r)] c) m [g + (v^2 / r)]

**Physics (I have a test tomorrow)**

the average speed of the car is 50 kph convert the speeds to m/s find the time to cover the 85 m find the change in kinetic energy ... KE = 1/2 m v^2 the work against resistance (friction) ... work = f d = 750 N * 85 m work and energy are the same thing add the work and the ...

**Physics**

the forces in c and d are normal (perpendicular) to the direction of motion of the car they do no work

**physics problem**

(2 * ? * 34 cm) / 39 m/s watch your units

**Science**

correct why the confusion?

**Science**

sounds like fermentation if there is oxygen, you get vinegar instead of wine

**math**

a- A = 12000 [1 + (.039/12)]^(6 * 12) b- subtract 12000 from a-

**maths**

no the ratio between the sides is not equal

**math**

A does 4/60 and B undoes 3/60 so 1/60 completed every 2 days after 112 days, 56/60 are done ... A completes the work on the 113th

**algebra**

6C3 ... 6! / (3! * 3!)

**Math**

it's a system of equations 5 V + 3 C + 2 M = 675 V = 2 C M = C + 75 substitute and solve

**Math**

x = 6 * 2^n

**physics**

cool the steam to 100ºC condense the steam cool the water to 0ºC freeze the water two specific heats heat of vaporization, and heat of fusion

**Math**

(300 / 500) * 250,000

**Physics 1401**

the center of mass of the stick is at the 50 cm mark ... 10 cm from the balance point the 6 g is 30 cm from the balance 10 * m = 30 * 6

**Physic sucks 1401**

the masses are linked by the string and have the same acceleration ... one upward and the other downward f = m a ... a = f / m (t - m1 g) / m1 = (m2 g - t) / m2 2t - 2g = 2g - t ... 3t = 4g ... t = 4/3 g the largest mass is 2 kg ... it gives about 20 N of force with the system...

**Geometry Proofs**

My teacher said she gave us everything.

**Geometry Proofs**

Trying to solve a proof. Triangle ABC. D is a point on side AC and E is a point on side BC. There is a line from Angle B to Point D and a line from Angle A to Point E. My Givens are AD = BE and BE>AE. I need to prove BC>AC. This is for my 7th grade geometry class. Thank ...

**Chemistry**

no some are not water soluble

**math**

look at 100,000 people 800 have it ... 56 will show negative ... 744 will show positive 99200 don't have it ... 2976 will show positive probability of accurate positive ... 744 / (744 + 2976)

**math**

(2 * 27.5) + 30/2

**Math - combinatorics/ permutations**

looks good

**Chemistry**

molarity is moles solute per liter of solution 0.05144 moles / .38 L = ? significant figures?

**science**

a + b = 29 a - b = 5 2a = 34 ... a = 17 ... b = 12 (17 + 3)^2 + (12 + 3)^2 = r^2

**Physics**

m g h + 1/2 m v^2 = 1/2 m V^2 (2 * 9.8 * 65) + 12^2 = V^2

**Mathematics.**

ER , 1/5 off , 4/5 normal , 80% normal ... normal = 64 / .80 MW , 15% off , 85% normal normal = 64.60 / .85