Tuesday

October 25, 2016
Total # Posts: 36,367

**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*

**Algebra**

let the three consecutive odd integers be x, x+2, and x+4 3x + 2(x+2) = 4(x+4) - 11 solve for x and sub into my definitions

*September 13, 2016*

**Math**

let the rate of growth be r then 326(1+r)^6 = 10,000 (1+r)^6 = 30.6748.. ( I stored it in memory for accuracy) take 6th root of both sides 1+r = 30.6748^(1/6) = 1.76928... or , using GS a = 326 r = ? 2004 ---> term 1 = a 2010 ----> term 7 = ar^6 326 r^6 = 10000 r^6 = ...

*September 13, 2016*

**Math pre algebra please help with ?**

1/2x -5 +2/3x=7/6x+4 multiply each term by 6 , the LCD 3x - 30 + 4x = 7x + 24 I am sure you can handle this equation.

*September 13, 2016*

**maths**

unit digit is x tens digit is x-5 the actual number is 10(x-5) + x the number reversed is 10x + (x-5) 10x + (x-5) - (10(x-5) + x) = 7 10x + x - 5 - (10x - 50 + x) = 7 11x - 5 - 11x + 50 = 7 45 = 7 , which is a contradiction There is no solution The question is bogus. e.g. ...

*September 13, 2016*