Thursday
September 29, 2016

Posts by Reiny

Total # Posts: 36,071

Math
hour hand: 8:00 am to 11:30 am is 3.5 hours. on the face of a standard clock this is 3.5/12 or 7/24 of a rotation, thus 105° or 7π/12 radians minute hand from 8:00 am to 11:30 am the minute hand will have made 3.5 rotations or gone through 1260° or 7π radians
September 18, 2016

Algebra
can't get any easier than this one. add them to find X then subtract them to get y
September 18, 2016

math
24=ax+4y-10 34 - ax = 4y y = (34-ax)/4 or 17/2 - ax/4 , looks like B
September 18, 2016

math
A=1/2h(b1+b2) 2A = hb1 + hb2 2A - hb2 = hb1 b1 = (2A - hb2)/h
September 18, 2016

Calculus 2
If N is the number of bacteria dN/dt = 20e^.8t N = 25 e^.8t + 50 when N = 700 700 = 25 e^.8t + 50 e^.8t = 26 take ln of both sides .8t = ln 26 t = appr 4.07 check: if t = 4.07 N = 25 e^.8(4.07) + 50 = 698.6 , not bad
September 18, 2016

math
so the area is x^2 and the perimeter is 4x area = (1/2)perimeter x^2 = 2x x^2 - 2x = 0 x(x-2) = 0 x = 2 or x = 0 , the latter makes no sense
September 18, 2016

math
Your question did not make sense the first time you posted it, that is why nobody has answered it. Are we supposed to see some kind of square? Does the x "in the square" represent the area or the length of the side? Awaiting your clarification so I can answer your ...
September 18, 2016

Math
All kinds of problems with this question. It is invalid to compare "interest paid" when you don't have the same focal dates. Are there monthly payments? I sure hope you weren't thinking of using simple interest. Since the interest rates are the same, the ...
September 18, 2016

Math
#1 y-5/3 =1 y = 1 + 5/3 = 8/3 , none of the given choices if you meant: (y-5)/3 =1 , which changes your question, y - 5 = 3 y = 8 #2 6x + 29 =5 6x = -24 x = -4 , choice A
September 18, 2016

math
To handle this type of equation you should be familiar with the steps to solve basic equations. K=3gy/(5f) multiply both sides by 5f 5f*K=3gy/(5f)*5f 5fk = 3gy divide both sides by 3y 5fk/(3y) = 3gy/(3y) 5fk/(3y) = g as shown above
September 18, 2016

math
I have a hunch you meant: K=3gy/(5f) based on that hunch .... 5fk = 3gy g = 5fk/(3y) those brackets are critical.
September 18, 2016

Math
"1 square mile wide and 1 square mile wide" makes no sense, there are no such units Does he have a field 1 mile by 1 mile ? make a sketch of a square 1 by 1 Divide the sides into 3 equal length and draw the dividing lines. You should have an X and O like game grid ...
September 18, 2016

math
All you have now three times in a row is to state an equation. What about it? Are you solving for one of the variables? Which one? Ms Sue already pointed this out to you when you were Carlos, but you stubbornly repeat it the same way. You did not ask a question!
September 18, 2016

Math
correct
September 18, 2016

Math
interest for 3 months = 20500(.043)(1/4) = 220.375 amount owing at that time = 20720.375 after payment of 7100, amount owing = $13,620.375 interest on the next 5 months = 244.03 debt at the end of that time = $13,864.41 after the 6900 payment, balance at the end of 8 months...
September 18, 2016

Equivalent Payments
done, see your later post of this
September 18, 2016

math
fee for Great Gym = 19.5m + 59 fee for wacky = 9.5m + 149 so you want 19.5m + 59 = 9.5m + 149 10m = 90 m = 9 it would take 9 months, cost = 19.5(9) + 59 = $234.50
September 18, 2016

Math
Look at Damon's correct solution to the one above this. I did not read the question carefully enough and proved that the sum of any 3 consecutive numbers is a multiple of 3. btw, that is also true for any 3 consecutive even numbers.
September 18, 2016

Math
any three consecutive numbers: x , x+1, x+2 their sum = x + x+1 + x+2 = 3x + 3 = 3(x+1) since it contains a factor of 3, it must be a multiple of 3
September 18, 2016

Math
According to your wording, (x^3 + 1) ÷ 1/x^3 which is (x^3 + 1)(x^3) = x^3(x+1)(x^2 - x + 1) , using the factoring of cubes principle
September 18, 2016

Math
With 4 coins, more heads than tails ---> 3H1T or 4H prob 3 of 4 heads = C(4,3)(1/2)^3 (1/2) = 4(1/8)(1/2) = 1/4 prob 4 out of 4 heads = (1/2)^4 = 1/16 prob(your event) = 1/4 + 1/16 = 5/16 aside: prob(no heads) = (1/2)^4 = 1/16 prob(1 head) = C(4,1)(1/2) (1/2)^3 = 1/4 prob(2...
September 18, 2016

Maths
Same question here, just the numbers are different, so change them to yours. go for it! http://www.jiskha.com/display.cgi?id=1474104642
September 18, 2016

MATHS
1(1.055)^n = 2 use logs n log 1.055 = log 2 n = log2/log1.055 = appr 12.9 years In the "olden days" we used something called the rule of 72 rate x time = 72 so here time = 72/5.5 = 13.09 , not bad
September 18, 2016

Maths
.7x = 77 x = 77/.7 = ...
September 18, 2016

calculus
Have you learned about Newton's Law of Cooling?
September 17, 2016

Geometry
Let M be (x,y) Make a sketch , draw two right-angled triangles, with hypotenuse AM = 3 and hypotenuse MB = 2 then use similar triangle ratios. for the x: (x-0)/20-x) = 3/2 2x = 60-3x 5x = 60 x = 12 for the y: (15-y)/(y-0) = 3/2 3y = 30 - 2y 5y = 30 y = 6 M is (12,6) or: the x ...
September 17, 2016

maths need help
Small codicil: The diameter is 40 m , not the radius
September 17, 2016

maths need help
I am puzzled by: There is a road of width 1 m starting from 1 m away of its end point.
September 17, 2016

Maths
you must have meant: If (x+3) varies directly as y then, x+3 = ky when x=3, y=12, so 6 = 12k k = 6/12 = 1/2 then x+3 = (1/2)y or 2x + 6 = y when "you" = 8 2x+6=8 2x=2 x = 1
September 17, 2016

Algebra
cost of 1 fillup = 16(2.11) = $33.76 monthly cost = 2(33.76) = $67.52 monthly allowance = 4(25) = $100 left over = 100 - 67.52 = $32.48 your answer is right
September 17, 2016

Trigonometry
In each of your problems the linear equation can be easily expressed in terms of y. Then sub that into the other equation I will do #2 from x-y = -3 y = x+3 subbing into the other: x^2 - x - (x+3) = 0 x^2 - 2x - 3 = 0 (x-3)(x+1) = 0 x = 3 or x = -1 if x = 3, y = 3+3 = 6 if x...
September 17, 2016

Algebra
any line parallel to the y axis has the form x = ?? look at the given point, what is the value of x ?
September 17, 2016

Maths
smaller part --- x larger part ---- 8 - x 7x^2 > 2(8-x)^2 by 13 7x^2 = 2(8-x)^2 + 13 7x^2 = 128 - 32x + 2x^2 + 13 5x^2 + 32x - 141 = 0 (x - 3)(5x + 47) = 0 x = 3 or x = -47/5 the two parts are either 3 and 5 or they are -47/5 and 87/5
September 17, 2016

Math
Tough question! roots are: x = ( -k-2 ± √(k+2)^2 - 4(k)(-3) )/2k = ( -k-2 ±√(k^2 + 4k + 4 + 12k))/2k it said: both x's are positive, so ( -k-2 + √(k^2 + 4k + 4 + 12k))/2k > 0 assuming we started with a positive x^2 term, so k > 0 -k-2...
September 17, 2016

math
John --- x Mary --- 2x Susan -- 2x x+2x+2x=150 solve for x, sub back into my definitions Just noticed that Ms Sue already did this for you.(Related Questions below) Always check back before reposting the same problem.
September 17, 2016

Maths
Both Steve and I answered this for you. What part of the answer did you not like ?
September 17, 2016

miss reiny correct-done
Ok, revising my difference calculations 1 3 2 6 3 1 11 5 2 1 19 8 3 1 31 12 4 1 48 17 5 1 ahhh, so the third difference is constant, so we have a cubic let the term = an^3 + bn^2 + cn + d when n = 1: 1 = a + b + c + d when n = 2 3 = 8a + 4b + 2c + d when n = 3 6 = 27a + 9b + ...
September 17, 2016

math
you have to know the rules of logs I will use: log (xy) = log x + log y log(x/y) = log x - log y log (x^a) = a log x Log72/75-log50/48+2log25/24 = log [ (72/75) ÷ (50/48) (25/24)^2 ] = log [ (72/75(48/50)(625/576) ] = log [1] = 0
September 17, 2016

arithemetic progression too hard help plz
* = 1st difference , ** = 2nd difference, *** = 3rd difference # * ** *** 1 3 2 6 3 1 11 5 2 1 31 20 15 13 48 17 -3 -18 You labeled you subject "arithmetic progression", so I expected a linear relationship. The first, second and third differences are NOT constants, ...
September 17, 2016

Math
let's place the smallest numbers in the most significant decimal places, so .01378 assuming we can use each digit only once.
September 17, 2016

Math
yes I boils down to simply showing that 9:6 ≠ 4:3
September 17, 2016

Math
when comparing ratios, it is often a good idea to have the parts represented by the same number. teacher: yellow : blue = 9 : 6 Gina: yellow : blue = 4 : 3 = 8 : 6 So, what do you think?
September 17, 2016

Math
let the parts be 2x, 3x, and 5x 2x + 3x + 5x = 5000 solve for x, sub back into my definitions
September 17, 2016

Math
1 : 5 = 8 : 40 If 1 ticket costs $5, how much will 8 tickets cost?
September 17, 2016

Math
well, if Pablo gets 1 free minute for every 5 paid, then he would get 8 free minutes for every 40 paid, Sam is getting only 25 paid minutes for every 8 free ones
September 17, 2016

math
new fraction = 13/15 change = 13/15 - 7/9 = .. if your answer is positive, the value of the fraction increased, if the result is negative, the function decreased. Try it with another fraction. What do you think the question is trying to show?
September 17, 2016

MATH
original loan: payment -- p i = .132/12 = .011 n = 288 PV = 21000 p( 1 - 1.011^-288)/.011 = 210000 I got p = $2413.34 balance after 68th payment = 210000(1.011^87) - 2413.34(1.011^87 - 1)/.011 = $195,059.83 new payment - 2413.3-500 = 1913.34 new i = .072/12 = .006 PV = 195059....
September 17, 2016

Maths
So we only have 8 digits to choose from for our leading digit, then 9 digits for each of the remaining spots number of three digit numbers with no 5 = 8x9x9 = 648
September 17, 2016

algebra
13 + [26 ÷ (−6 + 4 * 1)] = 13 + [26 ÷ (-2)] = 13 + [-13] = 0 Proof: http://www.wolframalpha.com/input/?i=13+%2B+((26+%C3%B7+(%E2%88%926+%2B+4+*+1))
September 16, 2016

geometry
Of course I am not just going to give you the answer. You have an isosceles triangle with a base of 12 and equal sides of 10 So sketch in the altitude, and you will have a right-angled triangle with base of 6, hypotenuse of 10 and the missing height Use Pythagoras to find that...
September 16, 2016

Math
We "solve" equations, but you don't have an equation. I will assume you have: x^2 + 3x + 1/4 = 0 yes, I would also multiply by 4 to get 4x^2 + 12x + 1 = 0 Unfortunately , it does not factor, so you will have to use the quadratic formula to solve it, or you can ...
September 16, 2016

math
LS = Log384/5+log81/32+3log5/3-log9 = Log384/5+log81/32+log5^3/3^3-log9 = log( (384/5)(81/32)(125/27)/9 ) = log(100) = 2 = RS
September 16, 2016

math
Log56/63-log100/108-log72/75 = log( (56/63)÷(100/108) ÷ (72/75) ) = log( (56/63)(108/100)(75/72) ) = log(1) = 0
September 16, 2016

Algebra homework
sketch a quarter circle with an outer radius of 16 and an inner radius of 4 So the area not wiped has to be subtracted form the area of the whole quarter circle, so ... find the area of 1/4 circle with radius 16 find the area of 1/4 circle with radius 4 subtract and you are ...
September 16, 2016

Math
looks like a decimal number with 2 decimal places 4.1x , sum has to be 10 , so 4.15 , 5.1x , ---> 5.14 6.1x, ---> 6.13 7.1x ----> 7.12 8.1x ----> 8.11 could it be 3 decimal places? 4.1xx --- 4.132, or 4.114 or 4.123 or 4.105 etc lot's of cases!
September 16, 2016

Math
number bought at each price ---- x of them so cost = x/10 + x/12 = 11x/60 selling price = 2x/15 difference = 2x/15 - 11x/60 = -x/20 , looks like a loss percent loss = (x/20) / (11x/60) = (1/20)(60/11) = .2727 or appr 27% check: suppose he bough 60 oranges at each price at 10 ...
September 16, 2016

maths
Let their respective prices be 16x and 23x new price of first horse = 1.1(16x) = 17.6x new price of second horse = 23x + 477 17.6x/(23x+477) = 11/20 352x = 253x + 5247 99x = 5247 x = 53 the first horse cost 16(53) or 848 the 2nd horse cost 23(53) or 1219 check: 848 : 1219 = 16...
September 16, 2016

math
first we have to find the payment. let it be p i = .07/12 = .005833.. ----> I stored in my calculator for increased accuracy PV = 220,000 n = 360 p( 1 - 1.0058333...^-360)/.0058333... = 220000 I got p = $1463.67 Value of debt if no payments had been made after 87 periods = ...
September 16, 2016

5th grade math
ONE ONE ----- TWO your answers don't work, since the starting digit of each of the two numbers must equal the unit digit of the answer, namely the O must be the same in all places. Your's isn't case#1 : let E = 1 then: 2N1 2N1 ---- 4W2, how about N = 3, can't ...
September 16, 2016

Math
Total sacks in the harvest ---- x number sold to nearby school = x/3 leaving them with 2x/3 amount used for food = (1/4)(2x/3) = x/6 leaving them with 2x/3 - x/6, or x/2 sacks to be sold to the pupils So .... 8000(x/2) = 216000 x = 2(216000)/(8000) = 54 sacks <---- total ...
September 15, 2016

Math
ten years ago: age of father --- x age of son ---- (1/5)x or x/5 5 years ago: father's age = x+5 son's age = x/5 + 5 son's present age = x/5 + 10 x/5 + 5 = (1/2)(x+5) multiply each term by 10, the LCD 2x + 50 = 5(x+5) 2x + 50 = 5x + 25 25 = 3x x = 25/3 or 8 1/3 ...
September 15, 2016

Calculus
A simple case of factoring will do the job limit (x^2 - a^2)/(x^4 - a^4) , x ---> a = lim (x^2 - a^2)/( (x^2 + a^2)(x^2 - a^2) = lim 1/(x^2 + a^2) , as x --> a = 1/(2a^2)
September 15, 2016

algebra
cost price --- x selling price = (2/5)x+100 (2/5)x + 100 = 8700 times 5 2x + 500 = 43500 2x = 43000 x = 21,500 check: (2/5)(21500) = 8600 which differs from her selling price by $100
September 15, 2016

algebra
P = .0445 x + 14.7 , where x is the number of feet of depth 32.5 = .0445x + 14.7 solve for x hint: comes out to a nice number
September 15, 2016

Math
amount of 60% stuff --- x ml amount of 30% stuff ---- 300 - x .6x + .3(300-x) = .45(300) .6x + 90 - .3x = 135 .3x = 45 x = 150 150 ml of the 60% solution and 150 ml of the 30% solution check .6(150) + .3(150) = 90+45 = 135 , as needed
September 15, 2016

Math
"B's collection of paper clips rose by 305 to 260" How can it rise by 305 to reach 260, unless there was a negative number of clips to start with ? bogus question.
September 15, 2016

Math
all perfect squares have pairs of equal factors e.g. 400 = 2x2 x 10x10 54 = 2 x 3 x 3 x 3 so we need another 2 and another 3 so the smallest number to be multiplied by 54 so it becomes a perfect square is 6 check: 6x54 = 324 = 18^2
September 15, 2016

Maths
What part of my previous reply to your post when you were Maria don't you like? http://www.jiskha.com/display.cgi?id=1473937034
September 15, 2016

vidya varthaka
1+cos² thetha =5/4 cos^2 Ø = 5/4-1 = 1/4 cosØ = ±1/2 angle in standard position is 30° but since cosØ is ±, Ø could be in any of the four quadrants Ø = 30°, 150°, 210°, 330° or Ø = π/6, 5&#...
September 15, 2016

maths need help
let 10^n = 2^1999 n log 10 = 1999log2 n = 601.7.. or appr 600 digits since 10^1 has 1 digit 10^2 has 2 digits etc
September 15, 2016

Math
Who knows. Depends on how many cats we have. If you meant, 24 cats line up for breakfast .... cat 1 eats 1 fish, total fish eaten = 1 cat 2 eats 2 fish, total fish eaten = 1+2 = 3 cat 3 eats 3 fish, total fish eaten = 3+6 = 6 cat 4 eats 4 fish, total fish eaten = 6+4 = 10 cat ...
September 15, 2016

Math
let brothers age last year be x then sister's age last year = 7x/8 brother's age now = x+1 sister's age now = 7x/8 + 1 = (7x+8)/8 we need one more piece of information to actually find the age. e.g. if brother last year was 8 then sister last year was 7 now brother...
September 15, 2016

math
"The number of girls on the two buses were equal" let the number of girls on each bus be x So the number of students on the nonAC bus = x+17 and the number of students on the AC bus = 73-x-17 = 56-x (3/5)(56-x) = x 168 - 3x = 5x 8x=168 x = 21 so on the AC bus we had ...
September 15, 2016

Maths
x ÷ (3/4) = 3 x(4/3) = 3 x = 9/4 check: (9/4) ÷ (3/4) = (9/4)(4/3) = 36/12 = 3
September 15, 2016

maths need help
make a sketch you will need the incentre of the triangle. This consists of the intersection of the angle bisectors label the triangle ABC, with the incentre O. Sketch in the three radii, hitting sides AB, BC, and CA at P, Q, R respectively. You should see that we have 3 pairs ...
September 15, 2016

math
see my reply to your earlier post of this http://www.jiskha.com/display.cgi?id=1473901698
September 14, 2016

math
See http://www.jiskha.com/display.cgi?id=1473903464 when you were Madison PS. by sheer coincidence "helppp's" solution is identical to mine.
September 14, 2016

Algebra
y = (-1/4)x + 648
September 14, 2016

trigonometry
cot^-1 27 is the angle Ø so that cotØ = 27 or tanØ = 1/27 my calculator gives me appr 2.12°
September 14, 2016

trigonometry
clear case of right-triangle trig height/65 = tan 35° height = 65tan35° = ....
September 14, 2016

math
correct
September 14, 2016

math
Just translate the English to Math let the number be x "Eleven more than twice a number has the same value as 8 times 'the difference of the number and 5" 11 + 2x = 8(x-5) solve for x , let me know what you got Hint: it is not a whole number
September 14, 2016

math
width--- x length --- 2x + 5 solve for x and sub into my definitions: 2x + 2(2x+5) = 232
September 14, 2016

math
According to my solution the 3 numbers are 55, 56, and 57 sum of the first two = 55+56 = 111 117 less than 4 times the larger = 4(57) - 117 = 111 Well, what do you know, it works
September 14, 2016

math
smallest number ---- x middle number ------ x+1 larger number --------x+2 x + x+1 = 4(x+2) - 177 2x+1 = 4x+8-117 -2x = -110 x = 55 the smallest is 55
September 14, 2016

math
Isabella's age --- x John's age ----- 2x - 17 x + 2x-17 = 40 solve for x and sub into my definitions
September 14, 2016

Math
"place-value reasoning" ? In my days we called it division, that is amount in each bag = 5.5/50 = .11 kg or 110 grams
September 14, 2016

correction - typo - math
x + 2x+5 = 17 3x = 12 x = 4 So Jessica is 4 and Sam is 13
September 14, 2016

math
Good grief, bobpursely gave a perfectly good answer when you posted as 8thgradestudent as did Graham http://www.jiskha.com/display.cgi?id=1473900151 please don't switch names, it causes the same question being answered unnecessarily . Here is another shot at it: Jessica&#...
September 14, 2016

math
Hey, it is your question, you typed it. I expressed my confusion of your typing. If 32800 are the school expenses, then we don't know his salary, let it be x after school expenses he has x - 32800 after spending 1/4 of that in savings he will be left with (3/4)(x-32000) or...
September 14, 2016

math
Hard to understand your typing. I assume the monthly salary is 32,000 and he used .2 of that for school fees, so he used 6400 for school fees, leaving him with 25,600 he used 1/4 of that to deposit, or he deposited 6400, leaving him with 19,200 for other expenses.
September 14, 2016

Math
Let the job of cleaning the room be 1 unit Tom's rate = 1/45 Wally's rate = 1/30 combined rate = 1/45 + 1/30 = 1/18 room/min job left to be done after 5 minutes = 1 - 5(1/18) = 13/18 let Gigi's rate be 1/x so total combined rate = 1/18 + 1/x = (x+18)/(18x) so (13/...
September 14, 2016

for Asha - maths
total value of his property ---- 60,000,000 wife's share = (1/5)(60,000,000) = 12,000,000 son & daughters share = 30,000,000 son's share --- 2x daughter's share --- x 2x + x = 30,000,000 x = 10,000,000 So the son gets 20,000,000 and the daughter gets 10,000,000 ...
September 14, 2016

Math
So for Sinea it was snacks : games : souv = 5 : 8 : 12 or 5x : 8x : 12x then ... 5x+8x+12x = 40 25x = 40 x = 1.6 Then Sinea spent the following: snacks = 5x = 8 games = 8x = 12.50 souvenirs = 12x = 19.20 Now repeat the same steps for Ren sn : ga : sou = 10 : 8 : 20 = 5 : 4 : ...
September 14, 2016

Math
What was the ratio ?
September 14, 2016

Math
speed of wind --- x km/h speed against the wind = 350-x km/h speed with he wind = 350+x km/h 169/(350-x) = 190/(350+x) cross-multiply and solve for x
September 14, 2016

Math
the number --- x its reciprocal --- 1/x x - 30/x = 1 times x x^2 - 30 = x x^2 - x - 30 = 0 (x - 6)(x + 5) = 0 x = 6 or x = -5, but a natural number is positive, so x = 6 check: 6 - 30(1/6) = 6 - 5 = 1 looking good.
September 14, 2016

math2
ax+by+c=0 ----> bx-ay+c=0 What that says is : interchange the coefficients of the x and y terms then change the sign of the y term to its opposite. Remember, it is considered to be "good form" to have the x term at the front as a positive term. e.g. 5x + 7y + 9 = ...
September 14, 2016

Math
S50E vs S40W Doesn't that form a 90° angle? So you have a right-angled triangle with legs of 7 and 24, and you are looking for the hypotenuse. Pythagoras anyone ?
September 14, 2016

Math
It asked for zebras : total = 2 : 16 = 1 : 8 , not 8 : 1
September 14, 2016

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