Sunday
December 4, 2016

Posts by Reiny

Total # Posts: 36,897

math
Hard to tell, since you did not define your x I will let Isabella's age be x years then John is 2x - 17 x + 2x-17 = 40 3x = 57 x = 19 So Isabella is 19, but it asked for John's age. John is 2(19) - 17 = 21
October 2, 2016

maths need help
(a/k)^y=k^m take log of both sides: y(log (a/k) = mlogk y(log a - logk = mlogk yloga = mlogk + ylogk yloga = logk (m+y) logk = yloga/(m+y) also: a^x = k^m xloga = mlogk logk = xloga/m xloga /m = yloga/(m+y) divide by loga x/m = y/(m+y) ym = x(m+y) ym = xm + xy ym - xm = xy m(y...
October 2, 2016

Algebra
Assuming you meant: 18-4x=6-6x 2x = -12 x = -6 Since we can't see any "following values of x" x = -6 better be part of the list
October 1, 2016

Math
circumference is a linear measurement, so you can immediately rule out any area or volume. the linear units I see are feet, metres, miles, and kilometres
October 1, 2016

Math
Only your last question is correct a) at least 2 blue ----> 2 blue, or 3 blue or 4 blue or 5 blue or total - 0 blue - 1 blue number with no restriction = C(19,5) = 11628 number with 0 blue = C(10,5) = 252 number with 1 blue = C(9,1) x C(10,4) = 1890 number with at least 2 ...
October 1, 2016

Math
I am sure you meant permutations. In a combination, the order does not matter, so there would be only one way For permutation, what is 3 x 2 x 1 ? check by listing them
October 1, 2016

Trigonometry
You should have learned that the slope of a line is equal to the tangent of the angle that line makes with the x-axis so slope = tan 60° = √3/1 = √3 so the equation is: y - 6 = √3(x - 2) y = √3 x + 6 - 2√3
October 1, 2016

Steve, Damon, bob - differential equations
The last time I did differential equations was 55 years ago, perhaps one of our other math tutors can kick in here
October 1, 2016

math
correct, except I would keep the k in the calculation old y = k x^2 new y = k (4x^2) change in y = 3k x^2 percentage change = 3k x^2/(k x^2) = 3 or 300% e.g. enter 1 and 4 for the following applet, http://www.marshu.com/articles/calculate-percentage-increase-decrease-percent-...
October 1, 2016

Probability
Damon's answer represents the prob of the particular order of AAAKK but it could have been AKAKA, etc that is, we have to multiply his product by 5!/(2!3!) btw, there are 52 cards in a deck, not 54 so his product is 4/52 x 3/51 x .... Once changed to that and multiplied by...
October 1, 2016

math
The question is not clearly stated. Ms Sue's answer is correct based on that interpretation I will interpret it that you want to know how many different teams of 5 students you can pick e.g. ABCDE would be a different team from ABCDF etc number of possible 5 member teams...
September 30, 2016

mathematics
first number ---- x second number ---- 2x-1 Their sum = 3x - 1 let's increase it by 2 ----> sum is now 3x + 1 3x+1 = 13 solve for x and all mysteries shall be revealed.
September 30, 2016

math
250/1200 = ???
September 30, 2016

quadratic functions
did you sub in your given value of t ? i.e. how about evaluating height = -16(1.5)^2 + 25(1.5) + 6 follow the instructions regarding rounding.
September 30, 2016

English - for Reiny
I have no idea what that means. Sounds like a Trump-like potpourri of word salad.
September 30, 2016

math
let the number who play both tennis and badminton be x then 45 = 30+26-x x = 11 badminton only ---> 30-11 = 19 tennis only ------> 26-11 = 15 Illustrate and confirm with a Venn diagram if you need to.
September 30, 2016

calculus help
I assume you meant: y=(cosxcosy-sinxsiny)/(sinxcosy+cosxsiny) = cos(x+y) / sin(x+y) , using your identities = cot(x+y) dy/dx = - csc^2 (x+y) (1 + dy/dx) dy/dx = -csc^2 (x+y) - dy/dx csc^2 (x+y) dy/dx + dy/dx csc^2 (x+y) = -csc^2 (x+y) dy/dx(1 + csc^2 (x+y) ) = -csc^2 (x+y) dy/...
September 30, 2016

maths
recall that any multiple of a Pythagorean triple is also a Pythagorean triple I know the "smallest" case is 3-4-5 so using 6 it would be 6-8-10
September 30, 2016

math
In one hour Kyle can do 1/3 yard In one hour Andres can do 1/4 yard so in 8 hours they can do 8(1/3) + 8(1/4) = 8(1/3 + 1/4) yards = 8( 7/12) yards = 14/3 yards or 4 2/3 yards They can do 14/3 yards (houses) in 8 hours then they can do 14 yards in x hours (14/3) / 14 = 8/x (14...
September 30, 2016

Math
Assuming you meant: (x+3)(3x^2 - 20x - 7) = 0 (x+3)(x-7)(3x+1) = 0 carry on
September 30, 2016

Math
common difference = 2k/3 - k = -k/3 given: 20th term is 15 so k + 19(-k/3) = 15 times 3, (I don't like fractions) 3k - 19k = 45 k = - 45/16 first term is -45/16 common difference = -k/3 = 15/16 term 6 = a + 5d = -45/16 + 5(15/16) = 15/8 term n = a + (n-1)d = a + nd - d = -...
September 30, 2016

Algebra
which property would apply to something like 5 x 6 = 6 x 5 ? I would immediately rule out A and D , since we are NOT adding.
September 30, 2016

Math
ok, looks like you are saying that you have a box with a square base of r inches each and a height of x inches volume = r^2 x = 78 so x = 78/r^2 cost = 4(area of base) + 3(4 sides) = 4r^2 + 12 rx = 4r^2 + 12(78/r^2)(r) = 4r^2 + 936/r b) makes no sense to me, since the volume ...
September 30, 2016

Math
original price --- $x after reduced price ---- 89% of x = .8x .8x = 13 solve for x by dividing both sides by .8
September 30, 2016

math
I don't see the choices you made for this assignment. So how can I check it ?
September 29, 2016

math
since it is linear, find the slope of the two ordered pairs that you have: assume 2007 ----> t = 0 then for 2012 , t = 5 slope = (28200 - 35250)/(5-0) = -1410 (interpretation: the town loses 1410 each year) so using the point (0,35250) the equation can be written as P = -...
September 29, 2016

Algebra
Do you like C(L) = .92L better? so the horizontal axis will be labeled L and the vertical axis as C(L)
September 29, 2016

Algebra
I just paid $11.04 for 12 litres of gas, while last week I paid $$59.80 for 65 litres of gas at the same price. If L is the number of litres, and C is the cost in dollars per L, find the equation for the cost in terms of L So you have 2 points of the form (L,C) and they are (...
September 29, 2016

Statistics
number of ways to choose first committee = C(18,6) = 18564 that leaves 12 people and we choose 7 of those = C(12,7) = 792 number of ways = 18564*792 = 14,702,688
September 29, 2016

math
Ok, I agree with your equation of y = (3/2)x + 2 well, if (50,p) lies on it, shouldn't it satisfy your equation? then p = (3/2)(50) + 2 = 75 + 2 = 77 check: http://www.wolframalpha.com/input/?i=plot+%7B(-2,+-1),+(4,+8)+,+(50,+75)%7D
September 29, 2016

math
amount invested at 6% ---- x amount invested at 8% ---- 3900-x .06x + .08(3900-x) = 280 times 100 6x + 8(3900-x) = 28000 continue
September 29, 2016

Algebra
width --- x twice the width --- 2x 5 more ----> + 5 5 more than twice the width = 2x + 5
September 29, 2016

Math
Did you mean: Two consecutive numbers with exact square roots that have a difference of 33 ? since all positive numbers has a square root make a list of perfect squares (they have an exact square root) 1, 4, 9, 25, 36, 64, 81, 100, 121, 144, 169, 196 , 225, 256, 289, .. ahh, ...
September 29, 2016

Math
by writing it as an exact fraction in the form 57/100
September 29, 2016

Pre-Calculus
for the first one: sin^2 Ø + cos^2 Ø = 1 divide each term by cos^2 Ø sin^2 Ø/cos^2 Ø + cos^2 Ø/cos^2 Ø = 1/cos^2 Ø tan^2 Ø + 1 = sec^2 Ø, (since 1/cosx = secx) do the 2nd by dividing each term by sin^2 &...
September 29, 2016

Pre-Calculus
tanØ = 1/2 sketch a right-angled triangle with base angle Ø, opposite as 1 and adjacent as 2 by Pythagoras, the hypotenuse^2 = 1 + 4 = 5 hypotenuse = √5 cosØ = 2/√5 secØ = √5/2
September 29, 2016

maths standard form
9*10^3 = 9000 So after 9002.05 is reduced by 9000 , we are left with 2.005 or 2 + .005 = 2*10^0 + 5*10^-3 so 9002.005 = 9*10^3+2*10^a+5*10^b = 9*10^3 + 2*10^0 + 5.0*10^-3 a=0 , b = -3
September 29, 2016

Math
Shiela's original amount --- x Rita's amount = 300-x after give-away: Shiela had x-56 Rita had 300-x + 56 = 356-x 356-x - 5(x-56) 356-x = 5x - 280636 = 6x x = 106 Shiela had $106 and Rita had $194
September 29, 2016

algebra
speed on first trip --- x km/h speed on return trip --- x-20 let the distance be d time for first part = d/x time for 2nd part = d/(x-20) d/x = 2 ---> d = 2x d/(x-20) = 3 ---> d = 3x - 60 3x-60 = 2x x = 60 So the distance each way was 120 km average speed = 240/5 = 48 km...
September 29, 2016

Algebra 1
amount = 4000(1.04)^3 I get $ 4499.46
September 29, 2016

Algebra 1
#1, they double ever 3 hours, so after 3 hours you would have 1000 after 6 hours you would have 2000 after 9 hours you would have 4000 or: number = 500(2^(t/3)) , plug in t = 9 #2, correct #3, 2.01 certainly IS a number between 1 and 10 so C
September 29, 2016

Math
none of the given choices represent 10/3 in any shape or form
September 29, 2016

MATH HELP!!
make a sketch to get a "feel" for the triangle a) find the slope of AB, AB, and BC. look for a pair of slopes that are negative reciprocals of each other. If you find such a pair, the the contained angle is your right angle. b) from you sketch you can decide which is...
September 28, 2016

geometry
umhh, they would have to be equal.
September 28, 2016

maths need help
nasty, nasty equation. You will have to resort to methods such as Newton's Method to solve simple but tedious and boring way: set your calculator to radians pick some values of x, e.g. let x = 1 LS = 150sin1 = 126.2... RS = 1 + 69.8 = 70.64 , nope let x = .5 LS = 150sin.5...
September 28, 2016

algebra
-7=11/17z multiply both sides by 17/11 -7(17/11) = (11/17)(17/11)z z = -119/11
September 28, 2016

algebra
let the distance be d miles time at 90 mph = d/90 time at 80 mph = d/80 d/80 - d/90 = 1 times 720 9d - 8d = 720 d = 720 miles
September 28, 2016

Pre-Calculus
csc Ø = √5/15 then sinØ = 15/√5 which is greater than 1, thus impossible. error in the question!
September 27, 2016

math
7d + 4h = 1400 4d + 7h = 1625 use elimination, multiply the first by 7 and the second by 4, the subtract. The h's will drop out I am sure you can handle it.
September 27, 2016

Math
not enough information. Is the large piece a square? If not, how are the length and width related. e.g. it could be 100 by 10, or 50 by 20, or ....
September 27, 2016

math
let speed of plane be x mph let the speed of the wind be y mph x+y = 510 x-y = 470 how about adding these two and see what happens.
September 27, 2016

MATH
no idea what /9 and /5 are supposed to be. I have an inkling you meant √9 and √5 of course √9 = 3, which is an integer.
September 27, 2016

Math
recall rate = distance / time rate = 90/1.9 ft/s = (90/5280) / (1.9/3600) mph = appr 32.3 mph
September 27, 2016

Pre-Calculus
cosØ = -√2/2 so Ø is in quadrants II or III you should know the trig ratios of the 45-45-90 as well as the 30-60-90 degree triangles. so you know the angle in standard position is 45°, because cos45 = √2/2 so Ø = 180-45 or 135° (in II) ...
September 27, 2016

Math~ Algebra 1
key concept: both would have covered the same distance let time of first car until catchup be t hrs let time of 2nd car until they meet be t-1 hrs 55(t-1) = 44t 55t - 55 = 44t 11t = 55 t = 5 distance = 5(44) or 4(55), same thing, = 220 miles
September 27, 2016

Pre-Calculus
csc Ø = 1.03 then sin Ø = 1/1.03 = appr .970873... make sure your calculator is set to radians Ø = 1.33 or π-1.33 = 1.8127 (in degrees, Ø = 76.14° or 103.86° ) Why were you unable to do that?
September 27, 2016

Math
7^-10 = 1/7^10 = ...
September 27, 2016

Math
the number is 4XX, 3XX, 2XX, 1XX or AB --- the number is a multiple of 6 multiples of 6 end in 6, 2, 8, 4, and 0 but it is NOT a multiple of 5, so that rules out the 0 ---- the tens digit is double the ones digit that rules out the 6 and 8 from the ones digit so the one's ...
September 27, 2016

brain teaser
number of sweaters ---- x number of skirts ------- y 3x + 2y = 3y 3x = y or x = y/3 so she has 3y to spend if she buys 1 skirt, or she spends y, that leaves her with 2y but y = 3x, so 2y = 6x = 6 sweaters check: suppose she has $90 so she can buy 3 skirts, each skirt would ...
September 27, 2016

Counting and Probability
Which 2 girls? Any two girls ? Can 3 girls or more sit beside each other, or only 2 girls? The wording is not specific enough. I will assume that we are talking about 2 specific girls, and instead of 9 chairs we have to arrange them in 8 ways. number of ways = 8! (suppose the ...
September 27, 2016

Math
a = 5 v = 5t + c when t = 0, v = 20 20 = 0+c ---> c = 20 then v = 5t + 20 when s is the distance, s = (5/2)t^2 + 20t + k when t = 0, s = 0 0 = 0 + 0 + k ---> k = 0 s = (5/2)t^2 + 20t how long did it take to go 10 m ? 10 = (5/2)t^2 + 20t 20 = 5t^2 + 40t t^2 + 8t = 5 I ...
September 27, 2016

maths
Just translate .... "pole C is 260 cm shorter than pole A" C = A - 260 but pole C = 1040 1040 = A-260 A = 1300 "pole A is twice as long as pole B" A = 2B 1300 = 2B B = 650 Now just add them up
September 27, 2016

math
In a parallogram, any two adjacent angles must add up to 180° so x + x+30 = 180 continue ....
September 27, 2016

Math
each brick has a volume of (6)(3)(2) inches^3 or 36 cubic inches so 1800 bricks would be 64,800 cubic inches you did not specify which units, so 1 cubic foot = 12^3 or 1728 cubic ft 1 cubic yard = 27 cubic ft use the above to convert to whichever units you need.
September 27, 2016

math
4.75 , I see 2 decimal places, so .. = 475/100 = 19/4
September 27, 2016

Maths
did you mean, find the number of subsets ? if so, there would be 2^5 or 32 of them, including the null set and the entire set
September 27, 2016

Maths
number that passed chemistry --- c number that passed biology ------ b sketch a Venn diagram, label the circles C and B place 8 in the intersection of the two circles place b-8 and c-8 in the parts of the circle not overlapping. so b-8 + 8 + c-8 = 60 b+c = 68 but it said: b = ...
September 27, 2016

Math
I don't understand. Didn't you state that the value of x is 75 ?
September 27, 2016

Math
how about 233 or 4211 or 2222 or 111,122 or ..
September 26, 2016

maths quartic equation need help
I just divided the quadratic that Steve found into the origianl quartic and got x^2 + 4x + 3 which factors to (x+1)(x+3) So the other two roots are -1 and -3
September 26, 2016

maths
total surface area = 2(7.2)(5) + 2(7.2)(3.32) + 2(5)(3.32) why are you using both a "," and a "." to represent the decimal place?
September 26, 2016

Trigonometry
Let the sides of triangle ABC be a, b, and c ,so that a is opposite angle A, etc we know a+b+c = 52, so c = 52-a-b sinA/sinB = a/b a/b = 3/4 4a = 3b---> b = 4a/3 sinA/sinC = a/c 3/6 = a/(52-b-a) 1/2 = a/(52-a-b) 2a = 52 - a - b 3a = 52-b 3a = 52 - 4a/3 9a = 156 - 4a 13a = ...
September 26, 2016

Algebra
your function will look like this: population = 56 e^kt, where t = 0 represents 1995 then 2002 ---> t = 7 and 2016 ---> t = 21 for t = 7 (2002) 59 = 56 e^7k 1.05357... = e^7k 7k = ln 1.05357.. = .052185753 k = appr .0074551 pop = 56 e^(.0074551t) sub in t = 21 and evaluate
September 26, 2016

math
You should first of all define x. If x is the amount left to be spent, then x+15 ≤ 60
September 26, 2016

math
cost price per apple = 1.2 they sold 70 at 1.5 or return = 105 profit = 5 percentage profit = 5/100 = .05 = 5%
September 26, 2016

Math
Traditionally, a line segment can be labeled by using the end points, such as AB where A is one end point and B is another If the direction you are going does not matter, AB would be the same as BA If direction is involved, we have something called a vector, but I don't ...
September 26, 2016

Math
376 , 377 , 378 ?? both 376 and 378 are multiples of 2
September 26, 2016

Math
my solution: let the other end point be (x,y) to get the x: (x+3)/2 = 5 x+3 = 10 x = 7 to get the y: (y+5)/2 = -11 x+5 = -22 y = -27 You had that, good job I agree, your teacher is in error.
September 26, 2016

Math
CD = 7-(-9) = 16 , or count them CE = (5/8)(16) = 10 now count over 10 units from C E ---> -9 + 10 = 1
September 26, 2016

Math
multiply the first by 3: 12x+9y=45 keep the 2nd 7x+9y=75 subtract them , (here is your elimination method) 5x = -30 x = -6 sub that back into the original 1st -24 + 3y = 15 3y = 39 y = 13 x = -6, y = 13
September 26, 2016

Math
I think you are having difficulty understanding the meaning of modular arithmetic I will use an example e.g. what is 15 mod 12 Think of a clock, after we have gone around counting the hours 1,2,3,... etc we start over again after 12 hours so it becomes obvious that 15mod12 = 3...
September 26, 2016

Algebra
clearly 7 x 10 or 70 tiles. Can you explain how I got that?
September 26, 2016

ALgebra
ages three years ago: Erna --- x Wendy --- 3x/4 Lucy ----- 2x/3 their ages now: Erna --- x + 3 Wendy --- 3x/4 + 3 Lucy ----- 2x/3 + 3 x + 3 + 3x/4 + 3 + 2x/3 + 3 = 67 x + 3x/4 + 2x/3 = 58 times 12, the LCD 12x + 9x + 8x = 696 x = 24 plug into my present age definitions.
September 26, 2016

Math
5 years ago: Lyn ---- x Anne -- 5x Now: Lyn = x+5 Anne = 5x+5 10 years from now: Lyn = x+15 Anne = 5x + 15 x+5 = (1/2)(5x + 15) 2x + 10 = 5x + 15 -3x = 5 solution makes no sense, the question is bogus.
September 26, 2016

math
total session including lunch = 13:00 - 9:30 = 4:00 session excluding lunch = 4:00 - .45 = 3:60 - 45 = 3:15 or 3 hours and 15 minutes
September 26, 2016

Math Need Help
why complicate things? wouldn't that just be ∫(4/(4-5x))dx = 4∫(1/(4-5x))dx = 4(-1/5) ln(4-5x) + c = (-4/5) ln(4-5x) + c
September 26, 2016

Math
do one step of a long division to get (x^2)/(x^2+1) = 1 - 1/(x^2+1) ∫(x^2)/(x^2+1)dx = ∫( 1 - 1/(x^2+1))dx = x - tan^-1 (x) + c , the last part should be part of your repertoire of integrals
September 26, 2016

Calculus
limit of (x^2 - 25)/(x^2 - 4x - 5) , as x --> 0 = lim(x+5)(x-5)/( (x-5)(x+1) = lim (x+5)/(x+1) , as x ---> 0 = 5/1 = 5
September 25, 2016

math
you will find this page perfectly suitable for your question http://davidmlane.com/normal.html
September 25, 2016

Math
No, one of your slopes is incorrect #3: 4x - y = 9 --> 4x - 9 = y , so the slope is 4 sum of slopes = -2 + 6 + 4 = 8
September 25, 2016

algebra
y=4x - 2 switch the variables x = 4y - 2 solve this for y 4y = x + 2 y = (x+2)/4 f^-1 (x) = (x+2)/4
September 25, 2016

algebra
g(6) = 3(6) - 5 = ...
September 25, 2016

Math
5 7/8 - 1/4 = 47/8 - 2/8 = 45/8 or 5 5/8
September 25, 2016

Absolute Inequalities
4-|2x-3| ≤ 9 -|2x-3| ≤ 5 |2x-3| ≥ -5 or by default: |2x-3| ≥ 0 , since the absolute value of anything ≥ 0 2x-3 ≥ 0 OR -2x+3 ≥ 0 x ≥ 3/2 OR -2x ≥ -3 x ≤ 3/2 so any value of x will work the solution is the set of real ...
September 25, 2016

Algebra 2
how about just subtracting 6y from both sides. See what your equation looks like. After that, I would also divide each term by 3 You should be able to do this in your head.
September 25, 2016

Urgent Math
let's take a look what we are dealing with http://www.wolframalpha.com/input/?i=plot+y+%3D-x%5E2+%2B+4x+%2B3+,+y+%3D+-x%5E3+%2B7x%5E2-10x+%2B+5 We can see that within your domain of 1 ≤x≤2 , they do not cross each other. so the effective height of our region...
September 25, 2016

correction - Math
since the tiles are 2 ft by 2 ft, and the room is 11 ft along one side, you will need 6 tiles along that side, with the last one to be cut along the 12 ft length, 6 tiles will fit, so you will need 36 tiles.
September 25, 2016

math
12 ft ÷ 7.5 inches = 144 inches ÷ 7.5 inches = 19.2 steps but the number of steps is a whole number. if we have 19 steps each would be 144/19 or 7.598 inches high, which is too high so we have to go with 20 steps, each one 7.2 inches high
September 25, 2016

math
What is a tossed altitude ? I will assume the question is as follows: Triangle ABC, AB = 15 , AC = 18 AD is an altitude where D is on BC and BD = 10 BD^2 + 10^2 = 15^2 BD = √125 = 5√5 similarly, CD = √224 = 4√14 BC = appr 26.147 cm Let the altitude from...
September 25, 2016

MATH 6grade
I now count 11 "Juan and his bookcase" questions. I don't think Juan will ever get it build.
September 25, 2016

  1. Pages:
  2. <<Prev
  3. 1
  4. 2
  5. 3
  6. 4
  7. 5
  8. 6
  9. 7
  10. 8
  11. 9
  12. 10
  13. 11
  14. 12
  15. 13
  16. 14
  17. 15
  18. Next>>