Thursday
August 25, 2016

Posts by Reiny

Total # Posts: 35,552

probability
what is 360/(360+318) ?
August 9, 2016

probability
what is (61/100)(640) rounded to the nearest whole number ?
August 9, 2016

probability
use the concept that Bob showed you here: http://www.jiskha.com/display.cgi?id=1470754142
August 9, 2016

Opt math URGENT
RS = (1/16)(-6cosØ) I picked a random angle, Ø = 25 LS ≠ RS the equation is not true, thus we can't prove the identity
August 9, 2016

Maths
routine right-angled triangle trig x/3.8 = cos 65 x = 3.8cos 65° take over
August 9, 2016

Math
4x + 3.0 = -4x + 2.6 4x + 4x = 2.6 - 3.0 carry on, it is easy
August 9, 2016

Math
Start with the unit x x 1 x 6 1 -2 6 1, no way x 7 2 -1 7 2 , no way x 8 3 0 8 3 , not really a 3 digit number >b>1 9 4 ---- looks good 1 10 5 , no way
August 9, 2016

Math
"of" usually means multiplication , not subtraction, so you want (1/8)(12) = 12/8 = 3/2
August 9, 2016

math
smaller number --- x next consecutive number ---- x+1 3(1/(x+1)) - 1/x = 3/10 multiply each term by 10x(x+1), the LCM 30x - 10(x+1) = 3x(x+1) 30x - 10x - 10 = 3x^2 + 3x 3x^2 - 17x + 10 = 0 (x - 5)(3x - 2) = 0 x = 5 or x = 2/3 but our number was to be an integer, so x = 5 the ...
August 9, 2016

Maths
one number ---- x , the larger the other --- 14-x x(14-x) = 40 14x - x^2 = 40 x^2 - 14x + 40 = 0 (x-10)(x-4) = 0 x = 10 or x = 4 the two numbers are 10 and 4.
August 7, 2016

Maths
No typo, the solution is correct first case was 2 years ago 2nd case is 6 years from now what is the time difference? Husnain, I even checked to show you that answer is correct.
August 6, 2016

Maths
2 years ago: Susie---- x Ronald --3x 6 years from now: Susie = x+8 Ronald = 3x + 8 3x+8 = 2(x+8) x = 8 2 years ago, Ronald was 24 So now he is 26 check: ages now: Ronals --- 26 Susie ---- 10 6 years from now Ronald will be 32 Susie will be 16 Ronald is twice as old as Susie, ...
August 6, 2016

ratio and proportions
number of rabbits ---- x number of cats ------- 2x number of dogs ----- 3(2x) = 6x 6x - 10 = x 5x = 10 x = 2 so 2 rabbits 4 cats 12 dogs
August 6, 2016

Math
S(1) = 1/(1*2*3) = 1/6 S(2) = 1/6 + 1/(2*3*4) = 1/6 + 1/24 = 5/24 S(3) = 5/24 + 1/(3*4*5) = 5/24 + 1/60 = 9/40 Wolfram said: http://www.wolframalpha.com/input/?i=1%2F(1*2*3)+%2B+1%2F(2*3*4)+%2B+1%2F(3*4*5)+%2B+...+%2B+1%2F(n*(n%2B1)*(n%2B2))
August 6, 2016

math
−4≤2x+6<18 subtract 6 -10 ≤ 2x < 12 divide by 2 -5 ≤ x < 6 remember, only multiplication and division by a negative number will affect the inequality sign. Since I multiplied by +2, nothing happened.
August 6, 2016

algebra
let's assume you have 1/√(x+1) multiply top and bottom by √(x+1) 1/√(x+1) * √(x+1)/√(x+1) = √(x+1)/(x+1)
August 6, 2016

math
correct
August 6, 2016

Algebra
If you meant: (1/2)x(2x-4)^2 = (1/2)(x)( 2(x-2) )^2 = (1/2)(x)(2^2)(x-2)^2 = (1/2)(x)(4)(x-2)^2 = 2x(x-2)^2 ----> that answer was correct or 2x^3 - 8x^2 + 8
August 5, 2016

Algebra
smaller number ---- x "The larger of two numbers is 5 less than twice the smaller number" ---> 2x - 5 Now just translate: "The sum " ---> + "The sum of [four times the larger] and [twice the smaller number] ---> 4(2x-5) + 2x " is 100"...
August 5, 2016

Incorrect Subject label - Maths
discussed here: http://www.jiskha.com/display.cgi?id=1412345782
August 5, 2016

ALGEBRA
this has been answered
August 5, 2016

A
Once you see the pattern, listing 7 numbers in each case is a trivial problem. Option 1 - they tell you the pattern Option 2 - square the numbers Option 3 - double the previous number
August 5, 2016

Math
6 workers do 1 km in 4 days 1 worker does 1 k m in 4/6 or 2/3 days 4 workers do 1 km in 8/3 days 4 workers do 3 km in 3(8/3) or 8 days
August 4, 2016

insight academy
amount invested at 10% -- x amount invested at 12% ---- 12000 - x .10x + .12(12000 - x) = 1280 easy to solve for x
August 4, 2016

Math
you probably meant: A= (x+4)/(xsquared+9x+20) = (x+4)/((x+4)(x+5)) = 1/(x+5) , x ≠ -4 B = (3xsquared-9x)/(xsquared+3x-18) = 3x(x - 3)/((x+6)(x-3)) = 3x/(x+6) , x ≠ 3 clearly they are not equivalent I am sure you can handle the algebra from this point.
August 3, 2016

math
value = mt + 1500 when t = 4, value = 800 800 = 4m + 1500 4m = -700 m = -175 value = -175t + 1500 plug in t = 5 to find value
August 3, 2016

someone please help me. - Precalc
y=cos(x−5π/2) amplitude = 1 period = 2π If we had the simple curve y = cos x the quarter points would be (0,1) , (π/2, 0) , (π, -1), (3π/2 , 0) , and repeating at (2π, 1) but we shifted our basic cosine curve 5π/2 units to the right, so...
August 3, 2016

Math
It says f'(x) = 2x-1 for x ≤ 1, so x = 1 is included and valid for f'(x) to get f'(1) = 1 for x ≤ 1, f(x) = x^2 - x + c which is a parabola opening upwards, we don't know c but notice that when x = 1 , f(1) = c so it "ends" at (1,c) for x&...
August 3, 2016

Math
height --- 4.9 base --- 3.9 area = (1/2)base x height = ...
August 3, 2016

Math Problem
lots of "dogs and chicken" problems listed below in Related Questions. Take a look at some of them
August 3, 2016

Math
Think about where the zeros can come from 1! = 1 , 2! = 2 , 3! = 6 , 4! = 24, 5! = 120 <-- our first zero ..... 10! = 3628800 <-- our 2nd zero that is, a zero comes from a number ending in 2 multiplied by a number ending in 5, or by a number ending in 0 so the zeros ...
August 3, 2016

maths
cost price ---- x final selling price = 1.04x but that represents 90% of the marked price so the marked price = 1.04x/.9 = 1.1555...x so the marked price is 15.55..% higher than the cost price. e.g. suppose the cost price is $100 marked up price = 100(1.155...) = 115.56 now ...
August 3, 2016

math
suppose you had 5 bags and each bag would contain 6 apples. How many apples would you have? What operation did you just perform? Do the same for your question.
August 3, 2016

calculus
height = -4.9t^2 + vt+ c but it said "groundlevel" ---> c=0 height = -4.9t^2 + vt 0 = -4.9(400) + 20v 20v = 1960 v = 98 So the initial velocity was 98 m/s height = -4.9t^2 + 98t d(height)/dt = -9.8t + 98 = 0 at maximum height -9.8t + 98 = 0 t = 10 seconds (We ...
August 2, 2016

Math
routine right-triangle trig. cos35° = 42/hypotenuse hypotenuse = 42cos35 = 34.4 ft to the nearest whole number, 34 ft
August 2, 2016

math
It gets even more complicated when you consider that more than likely compound interest would have been used. So at what rate are 24 payments equivalent to a present value of 3438 ? 165(1 - (1+x)^-24)/x = 3438, where x is the monthly rate tough to solve, used Wolfram: http://...
August 2, 2016

maths
number of boys ---- b number of girls ----- g b = 4g + 3 b-3 = 4g g= (b-3)/4 e.g. let the number of boys be 43 then girls = (43-3)/4 = 10 4 times the number of girls plus 3 = 4(10)+3 = 43 which is the number of boys
August 2, 2016

Math
They would be separating at 500 ft/min time to go 3000 ft at that speed = 3000/500 min or = 6 minutes or time taken --- x minutes distance of one student = 300x distance of other student = 200x 300x + 200x = 3000 500x = 3000 x = 6 , just like above.
August 2, 2016

Math
1 L take you 64/7 km 9/8 L take you (64/7) * (9/8) or 72/7 km or 10 2/7 km = appr 10.29 km again, I repeat my concern about decimals vs fractions. First of all you rounded off intermediate answers, so the error just gets compounded
August 2, 2016

Math
40 5/6 = 240/6 + 5/6 = 245/6 review how to change a mixed fraction to a usable fraction.
August 2, 2016

Math
(5/9) / x = (245/6) / 1 245x/6 = 5/9 245x = 6(5/9) = 10/3 x = 10/735 = 2/147 or appr .0136 1 cm^3 weighs 2/147 kg you are correct, notice that since the original data was given in exact fractions, it might be a good idea to state the answer as a fraction
August 2, 2016

Opt math
Let ABC be a right-angled triangle with ∠ABC = 60° and ∠CAB = 30°. Let ABD be a right-angled triangle on the same side of AB with ∠ABD = 40° and ∠DAB = 50° Suppose that AC and BD intersect at E, and that the length of BC is 1, so that ...
August 2, 2016

Math
25x³-36x step1, common factor = x(25x^2 - 36) step2, recognize the difference of squares = x(5x-6)(5x+6)
August 2, 2016

maths
original price ---- x reduced price = .8x number of kg purchased at original price = 160/x number of kg purchased at reduced price = 160/(.8x) 160/(.8x) - 160/x = 2/5 200/x - 160/x = 2.5 40/x = 2.5 2.5x = 40 x = 16 find the original rate ???? the reduced price = .8(16) = 12.8...
August 2, 2016

maths
I sure hope these are not US or Canadian dollars. number of kg of expensive : cheaper = 5x : 2x cost = 250(5x) + 75(2x) = 1400x selling price = 230(7x) = 1610x percent gain/loss based on cost price = (1610x - 1400x)/(1400x) = 210/1400 = .15 profit is 15%
August 2, 2016

math
If the question had the dimensions are whole numbers. How about x = appr 1.98 ? http://www.wolframalpha.com/input/?i=2(x(2x)+%2B+x(x%2B2)+%2B+2x(x%2B2))+%3D+63
August 2, 2016

Math
number of ducks ---- d number of goats ----- g d + g = 30 , they have 1 head each 2d + 4g = 94 or d + 2g = 47 subtract the two equations: g = 17 the d + 17 = 30 ----> d = 13 state the conclusion
August 2, 2016

maths
What is 1 - (.8)(.9) as a percentage ?
August 2, 2016

maths
find the original rate ? you meant: find the original price ? let original price be x .8x = 160 x = 160/.8 = 200 but that is for 2.5 kg so original price per kg = 200/2.5 = 80 reduced price per kg = 160/2.5 = 64 notice that 64 equals 80% of 80
August 2, 2016

Math 6th Grade
the LCM ≥ GCF So the only cases to get a product of 12 is: 12 1 6 2 4 3 suppose we have a LCM of 12 and a GCF of 1 how about 12, 1 coming from 3,4 checking: so the number pair (3,4) has a LCF of 1 , and a HCM of 12, product is (1)(12) = 12 looks good! does 6,2 work? LCM...
August 2, 2016

maths
total time = 5 hrs, 15 minutes = 5.25 hrs let the total journey be 2x time at 60 km/h = x/60 time at 45 km/h = x/45 x/60 + x/45 = 5.25 = 21/4 times 180 , the LCD 3x + 4x = 945 7x = 945 x = 135 total distance = 2x = 270 km check: 135/60 = 9/4 hrs 135/45 = 3 hrs total time = 9/4...
August 2, 2016

maths
let the travel time be t hrs let the stoppage time be s hrs without stopping, distance = 60t with stops, distance = 40(t+s) 60t = 40t + 40s 20t = 40s t = 2s So for any given time, the train spends twice the time driving as it does stopping or in hour , the time stopping is 20 ...
August 2, 2016

Math
brother's age ---- x Lily's age ------- x+ 14 8 years from now: brother's age = x+8 Lily's age = x+14 + 8 = x + 22 x+22 = 2(x+8) solve for x and sub into my definitions
August 1, 2016

Calculus
find their intersection x^2 - 4x + 1 = -x^2 + 4x - 5 2x^2 - 8x + 6 = 0 x^2 - 4x + 3 = 0 (x-1)(x-3) = 0 x = 1 or x = 3 look at http://www.wolframalpha.com/input/?i=y+%3D+x%5E2+%E2%88%92+4x+%2B+1+,+y+%3D+%E2%88%92x%5E2+%2B+4x+%E2%88%92+5 As you can see, they cross at (1,-2) and...
August 1, 2016

algebra quadratic equations
base --- x height = x-1 area of triangle = (1/2) base x height (1/2)(x)(x+1) = 105 x^2 + x = 210 x^2 + x - 210 = 0 (x+15)(x-14) = 0 x = -15 or x = 14, but x > 0 base is 14 cm, height is 15 cm check: area = (1/2)(15)(14) = 105 all is good!
August 1, 2016

maths
after markup ---- > 140% after discount --- .75(140)% = 105% so the trader makes a profit of 5%
August 1, 2016

maths
right now: number of girls ---- x number of boys --- x+15 after increase: girls ---- 1.15x boys ---- 1.2(x+15) boys - girls = 29 1.2(x+15) - 1.15x = 29 1.2x + 18 - 1.15x = 29 .005x = 11 x = 220 there are 220 girls and 235 boys or a total of 455 students check: 1.2(235) = 282 1...
August 1, 2016

math
I do not understand the question.
August 1, 2016

Calculus
Let the right-hand corner vertex be P(x,y) but 3x+2y = 1 y = (1-3x)/2 or 1/2 - (3/2)x area = xy = x(1/2 - (3/2)x) = (1/2)x - (3/2)x^2 d(area)/dx = 1/2 - 3x = 0 for a max of area 3x = 1/2 x = 1/6 y = 1/2 - (3/2)(1/6) = 1/4 ---> P is (1/6 , 1/4) max area = xy = (1/6)(1/4) = 1...
August 1, 2016

PreCalculus
You didn't define your x and y, but I will assume that they represent length and width. So your first equation of xy = 30 is correct Your second equation makes no sense I will let x be one of the sides costing $55/ft From the data, I get Cost = 40x + 15(x+2y) = 40x + 15x...
August 1, 2016

Math
13/9 + 10/3 + 4 = 13/9 + 30/9 + 36/9 = ...
August 1, 2016

maths
The slope of a line equals tan A, where A is the angle that the line makes with the x-axis So the slope of your line is tan (-135°) = 1 then y = x + b but (3,4) lies on it, ... 4 = 3 + b b = 1 y = x + 1 or x - y = -1
August 1, 2016

math (integral)
You probably meant y=e^(-x^2) look at the graph http://www.wolframalpha.com/input/?i=y%3De%5E(-x%5E2) the maximum ordinate is y = 1 however, the function never reaches the x-axis, so there is a "gap". Unless you left out some vertical boundaries, the question is bogus.
July 31, 2016

math (integral)
Did you mean y = ln x ? , I will assume you did Make a sketch to see the region in question. so you want ∫ lnx dx from x = 1 to e = [xlnx - x] from 1 to e = elne - e - (1ln1 - 1) = e - e - 0 + 1 = 1 (the integral of lnx should be in your repertoire of standard integrals)
July 31, 2016

Math
not enough information: Are the chairs in a line? Are the chairs in a circle? Suppose they are in a line. Number of ways to choose 5 of the 8 chairs to seat the boys = C(8,5) = 56 but for each of those choices, we can arrange the 5 boys in 5! ways. number of ways to seat 5 ...
July 31, 2016

maths
We could do it algebraically but there are so few choices, let's just take the cases. "its unit's digit exceeds twice its ten's digit by 2" ---> 14, 26, 38, 4x, the x would have to be 10 so 14, 26, or 38 in which of these do we get a product of 24 from...
July 31, 2016

algebra
x^2 + x^2/(x+1)^2 = 3 times (x+1)^2 x^2(x+1)^2 + x^2 = 3(x+1)^2 x^2(x^2 + 2x + 1) + x^2 = 3(x^2 + 2x + 1) x^4 + 2x^3 + x^2 + x^2 = 3x^2 + 6x + 3 x^4 + 2x^3 - x^2 - 6x - 3 = 0 nasty equation, so I tried Wolfram, http://www.wolframalpha.com/input/?i=x%5E4+%2B+2x%5E3+-+x%5E2+-+6x...
July 31, 2016

kaushik
Simple interest or compound interest? at simple interest, let the original be $x change our times to months ---> 2 yrs, 3 months = 27 months interest = x(.11)(27/24) = 99x/800 x+99x/800 = 4491 x(1 + 99/800)= 4491 x = 3996.44 in 3 years: amount = 3996.44 + 3996.44(.11)(3) = ...
July 31, 2016

math
assuming log2 (4y) means log2 (4y) I could write 5 as log2 32 so we have: 5 - log2 (4y) = log2 32 - log2 (4y) = log2 (32/(4y)) = log2 (8/y)
July 30, 2016

pre algebra
let the smaller be x let the larger be 44+x translate: "Five times the smaller is equal to 8 more than the larger" ----> 5x = 44+x + 8 4x = 52 x = 52/4 = 13 smaller is 13 , larger is 57 check 57-13 = 44 , check!! 5 times the smaller is 65 is 65 greater than 57 by ...
July 30, 2016

math
one number .... x other numbr .... 2x + 3 x(2x+3) = 35 2x^2 + 3x - 35 = 0 it factors .... (2x-7)(x+5) = 0 x = 7/2 or x = -5 but since the numbers are negative x = -5 one number is -5 the other is -7
July 30, 2016

Calculus AB
From you subject title, I will assume you have studied vectors. let r be the resultant vector 40 min at 3.5 mph = 7/3 miles 20 min -----> 7/6 miles 60 min -----> 7/2 miles 15 min -----> 7/8 miles r = ((7/3)cos0, (7/3)sin0) + ((7/6)cos245, (7/6)sin245) + ((7/2)cos345...
July 30, 2016

Calculus AB
So the other angle must be 180-2(55) or 70° draw in the height, h You now have a right-angled triangle, let the hypotenuse be x you can find the height by tan 55° = h/10 you can find the side by cos 55° = 10/x once you have x, you can find the perimeter. once you ...
July 30, 2016

Calculus AB
That was my answer.
July 30, 2016

Calculus AB
If you make a good sketch , this is not that hard I labeled the cars as A for the farther none, and B as the closer one. Let C be the base of the building So we want to find AB Two right-angled triangles, were clearly the angle at A is 29.5° and the angle at B is 38.2°...
July 30, 2016

Calculus AB
Let's visualize what we have here: recall that cos Ø = adjacent/hypotenuse and arccos((x+1)/2) mean we have an angle Ø so that cos Ø = (x+1)/2 so construct a right-angled triangle with base of x+1 and hypotenuse 2 and base angle of Ø Let the ...
July 30, 2016

Math
4*15-11+8-2 = 55
July 30, 2016

Maths
just plug in n = 1, n = 3, n = 5 If will do the n = 3 S(n) = 3(3) - 2 = 7
July 30, 2016

Math
Probably meant to type: x= 2-3t, y= -1+5t from x= 2-3t, -----> t = (2-x)/3 rom y= -1+5t ---> t = (y+1)/5 (2-x)/3 = (y+1)/5 3y+3 = 10 - 5x 5x + 3y = 7 slope = -5/3
July 30, 2016

Math
What is a "po" ?? are we solving 4(4x)^2 + 2(4x) + 5 = 0 ?? (we "solve" equations, you had no equation) let 4x = y, so your equation becomes 4y^2 + 2y + 5 = 0 y = (-2 ± √-76)/8 = (-2 ± 2√19 i)/8 = (-1 ± √19 i)/4 4x...
July 29, 2016

MATH
the way you typed it ... a = -(1)^n 1^anything = 1 so a = -1
July 29, 2016

math
a=2/3b 3a = 2b b = 3a/2 c=3/2b 2c = 3b b = 2c/3 thus: 2c/3 = 3a/2 4c = 9a 4/9 = a/c a : c = 4 : 9 notice 2/3b ≠ 2/(3b) I assumed you meant it the way you typed it.
July 29, 2016

statistics
it said "without replacement" , so the prob that the second is faulty is not 15% Bernie, what part of my solution did you not like ? http://www.jiskha.com/display.cgi?id=1469831346
July 29, 2016

math
There are actually more than what I gave you. Mine are only from the addition of these angles. How about subtractions ? e.g. 45 - 30 = 15 Can you find some more?
July 29, 2016

math
How would you get 145°
July 29, 2016

math
mmmh??? I could do a 30°, 45°, 60° , 90° , 75°, 105°, 120°, 135°, 150°, 165° Can you see any I missed ?
July 29, 2016

Maths
My assumption is that this question contains a typo. The effect is that I can't do the question.
July 29, 2016

math
complementary angles add up to 90° let the two angles be 3x and 2x, then their difference is x but 3x + 2x = 90 5x = 90 x = 18 the difference in the two angles is 18° check: one is 3(18) = 54 the other is 2(18) = 36 and what is their difference ??
July 29, 2016

Math
width ---- w length ---- w+5 P = 2w + 2(w+5) = 2w + 2w + 10 = 4w + 10 4w + 10 ≤ 150 4w ≤ 140 w ≤ 35 max width is 35 m
July 29, 2016

Math
I am a bit confused myself, unless you have a typo. I will assume you meant your first set to be x = 3-2t, y = -2 + 5t so -1+ 3s = 3 - 2t ---> 2t + 3s = 4 ** and -2 + 5t = 5 - 9s ---> 5t + 9s = 7 *** 3 times ** ---> 6t + 9s = 12 subtract *** t = 5 back in ** 10 + 3s...
July 29, 2016

statistics
done, look back
July 29, 2016

statistics
prob = (3/20)(2/19) = 3/190 same question as: I have 20 marbles of which 3 are red I choose 2 without replacement, what is the probability that they are both red
July 29, 2016

math
So we need a triangle with area of 30 cm^2 let the length of each of the equal sides of the isosceles triangle be x, and the height be h h^2 + 6^2 = x^2 ** but we also know that the area of the triangle is (1/2)(12)h = 30 6h = 30 h = 5 then in ** 25 + 36 = x^2 x^2 = 61 x = &#...
July 29, 2016

math
By the definition of a rhombus , all sides are equal, so if one side is 10, then all sides are equal to 10. Also, the diagonals bisect each other at right angles creating 4 congruent right-angled triangles. Looking at one of these triangles, we have sides 3x, 4x, and ...
July 29, 2016

oops - Calculus
dont' know where the 65 came from simply change it to 64 and complete the solution, you should get 48 and 16
July 28, 2016

Calculus
A product is the result of a multiplication. "product of one of them plus the cube of the other" is mathematically confusing, since "plus" implies addition. I will assume you meant: "product of one of them with the cube of the other" let the one ...
July 28, 2016

maths
(3-√-16) = 3 - 2i recall: √-1 = i √-16 = √4 x √-1 = 2i
July 27, 2016

Math
let the two numbers be x and x+1 x + x+1 = S 2x = S - 1 x = (S-1)/2 The square of the larger number minus the square of the smaller number = (x+1)^2 - x^2 = x^2 + 2x + 1 - x^2 = 2x + 1 = (S-1) + 1 = S check: let's take 37, and 38 sum = 75 square of larger =1444 square of ...
July 27, 2016

Math
15/4 = 3.75 or = 3 3/4 as a mixed fraction or how about (1/2)(7.5) or (1/4)(15 or .....
July 27, 2016

GP
so the GP terms are: a+d, a+3d, and a+6d (a+3d)/(a+d) = (a+6d)/(a+3d) (a+6d)(a+d) = (a+3d)^2 a^2 + 7ad + 6d^2 = a^2 + 6ad + 9d^2 ad = 3d^2 divide by d a = 3d common ratio : r = (a+3d)/(a+d) = 6d/(4d) = 3/2
July 27, 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>>