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# Recent problems solved by 'ewatrrr'

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 Finance/610123: How long will it take to triple a savings of \$5000.00 at 2.5% annual interest compounded continuously 1 solutions Answer 384153 by ewatrrr(10682)   on 2012-05-12 07:06:34 (Show Source): You can put this solution on YOUR website! ``` Hi, In General for Cases where Interest compounds Contiuosly A = Accumulated Amount \$15000 P= principal = \$5000 r= annual rate = .025 t= years = ln3/.025 = t = 43.9 yrs ```
 Radicals/610130: five rational number between -4 ad -21 solutions Answer 384152 by ewatrrr(10682)   on 2012-05-12 07:01:23 (Show Source): You can put this solution on YOUR website! ``` Hi, five rational number between -4 ad -2 -2.25, -2.5,-3, -3.5,-3.75 ```
 Linear-systems/610133: Solving for... 4x-3y = 10 x+4y = 7 Using any methood... Solution: x = 3.21052631578947, y = 0.947368421052632 However (1, -2) also works why? How can I solve this system and yeild the possible result (1, -2)? 1 solutions Answer 384151 by ewatrrr(10682)   on 2012-05-12 06:53:36 (Show Source): You can put this solution on YOUR website! ``` Hi, Re:Your TY (1, -2) 4x-3Y=10 or 4*1+3*2=10 4+6=10 Yes x+4y=7 or 1+4*(-2)=7 1+(-8)=7 No: -7 ≠ 7 Might Check Your Sign in EQ II: would yield the solution (1,-2) , y = -2 and x = 1 I. 4x-3y = 10 II. x+4y = 7 ||Signs SO important to the Solution 4x-3y = 10 -4x-16y = -28 -19y = -18 y = 18/19 = 0.947368421052632 and x = 3.21052631578947 (1,-2) is a Pt on the fist line, not the 2nd line. The Solution for this system of Two EQ, is as You found: x = 3.21052631578947, y = 0.947368421052632 ```
 Problems-with-consecutive-odd-even-integers/610037: . The sum of the reciprocals of two consecutive positive odd integers is 16/63. Find the integers.1 solutions Answer 384093 by ewatrrr(10682)   on 2012-05-11 18:54:29 (Show Source): You can put this solution on YOUR website! ``` Hi, The sum of the reciprocals of two consecutive positive odd integers is 16/63 63(n+2) + 63n = 16n(n+2) |||Multiplying thru by 63n(n+2) so as all denominators = 1 16n^2 - 94n - 126 = 0 n = 7, tossing out negative solution 7 and 9 are the two consecutive positive odd integers CHECKING our Answer*** 1/7 + 1/9 = 16/63 ```
 Rational-functions/609956: triangle ABC has vertices A(-1,2) B(1,5) C(5,2). Draw the graph of the triangle and find the area.1 solutions Answer 384092 by ewatrrr(10682)   on 2012-05-11 18:41:55 (Show Source): You can put this solution on YOUR website! ``` Hi, triangle ABC: vertices A(-1,2) B(1,5) C(5,2). A = (1/2)bh = (1/2)6·3 = 9 units^2 ```
 Probability-and-statistics/609989: I have 8 cans of soft drinks, 4 different brands with 1 regular and 1 diet for each brand. I arrange 4 cans in a row randomly. Find probability that first two are diet and second two are regular? [I know the anser is 3/35, but I'm not sure how to get this using the combination of 2 out of 4 for regular, and 2 out of 4 for diet. Thanking you in advance for the direction!] DCM 1 solutions Answer 384089 by ewatrrr(10682)   on 2012-05-11 18:34:13 (Show Source): You can put this solution on YOUR website! ``` Hi, 8 cans of soft drinks, 4 different brands with 1 regular and 1 diet for each brand.(4 diet and 4 regular) 4 cans in arranged in a row randomly. P(first two are diet and second two are regular) ```
 Expressions-with-variables/610028: Find the value of x so that the line joining the points(x,3)and (2,1)is parallel to the line joining (x,5)and (-1,2)1 solutions Answer 384087 by ewatrrr(10682)   on 2012-05-11 18:24:18 (Show Source): You can put this solution on YOUR website! ``` Hi, Find the value of x so that the line joining the points(x,3)and (2,1)is parallel to the line joining (x,5)and (-1,2) Note: slopes Equal (x,3)and (2,1) (x,5)and (-1,2) ||Cross Multiplying to solve 3(x-2) = 2(x+1) x = 8 ```
 Probability-and-statistics/609974: An aviary contained 12 birdies and 15 eagles. Bogey left the window open and before Paar shut it, seven of them had flown out. Find the probability that 4 birdies and 3 eagles escaped through the window in alternating order. 1 solutions Answer 384085 by ewatrrr(10682)   on 2012-05-11 18:18:38 (Show Source): You can put this solution on YOUR website! ``` Hi, An aviary contained 12 birdies and 15 eagles. BIRDS in all. seven of them flew out. P(4 birdies and 3 eagles escaped through the window in alternating order) P = ```
 Probability-and-statistics/610021: A random sample of 33 adult men had a mean weight of 182.5 pounds and a standard deviation of 22.5 pounds. Find a 99% confidence interval for the mean weight of adult men. 1 solutions Answer 384082 by ewatrrr(10682)   on 2012-05-11 18:09:22 (Show Source): You can put this solution on YOUR website! ``` Hi, 33 adult men had a mean weight of 182.5 pounds and a standard deviation of 22.5 pounds ME = 2.576*22.5/sqrt(33) = 10.1 CI: 182.5-10.1 < u <182.5 +10.1 CI: 172.4 < u <192.6 ________________________________________________________________________________ a a/2 crtical regions 80% 0.2 10% z <-1.28155 z >+1.28155 90% 0.1 5% z <-1.645 z >+1.645 92% 0.8 4% z <-1.751 z >+1.751 95% 0.05 2.50% z <-1.96 z >+1.96 98% 0.02 1% z <-2.33 z >+2.33 99% 0.01 0.50% z<-2.576 z >+2.576 ```
 Polynomials-and-rational-expressions/610005: Factor out the Greatest common monomial factor 1.4xsquared + 6xy 2. 18ysquared + 6yz 3. 2x +2y 4. 15asquaredbsquared +5ab 5. 5xy-12x Thanks!!1 solutions Answer 384072 by ewatrrr(10682)   on 2012-05-11 17:18:12 (Show Source): You can put this solution on YOUR website! ``` Hi, The Idea is to factor out what the two terms have IN COMMMON... ||NOTE: 2x·2x = 4x^2 2x +2y = 2(x+y) 5xy-12x = x(5y-12) ```
 Volume/610012: find the volume of a cylinder with a base of 25pi in^2 and height equal to the radius. Give your answer in terms of pi or rounded to the nearest tenth.1 solutions Answer 384071 by ewatrrr(10682)   on 2012-05-11 17:11:42 (Show Source): You can put this solution on YOUR website! ``` Hi, base = in^2, r = 5 height equal to the radius. V = ```
 Exponents-negative-and-fractional/610022: What is 3/20 of 64 ( what is three/twentieth of 64?)1 solutions Answer 384070 by ewatrrr(10682)   on 2012-05-11 16:58:53 (Show Source): You can put this solution on YOUR website! ``` Hi, 3/20 'of' 64 = = 96/10 = 9.6 ```
 Volume/610015: find the volume of a cone with a basic circumference of 19pi cm and a height 6cm less than twice the radius. Give your anwser in terms of pi or rounded to the nearest tenth.1 solutions Answer 384069 by ewatrrr(10682)   on 2012-05-11 16:54:24 (Show Source): You can put this solution on YOUR website! ``` Hi, cone with a basic circumference of 19pi cm and a height 6cm less than twice the radius C = r = 19/2 and r^2 = 90.25 V = ```
 logarithm/609990: log2+logx=1og32 I just dont understand Logarithms.1 solutions Answer 384064 by ewatrrr(10682)   on 2012-05-11 16:09:21 (Show Source): You can put this solution on YOUR website! ``` Hi, log2+logx=1og32 = 2x = 32 x = 16 Basic facts about Logarithms: ********* ***** ```
 Surface-area/609936: 1) A rectangular garden is 9 ft longer than it is wide. Its area is 486 ft2. What are its dimensions? 1 solutions Answer 384052 by ewatrrr(10682)   on 2012-05-11 14:34:31 (Show Source): You can put this solution on YOUR website! ``` Hi, Note: Category Change A rectangular garden is 9 ft longer than it is wide Let w and (w+9) represent the width and length respectively Question states***area is 486 ft2. w(w+9) = 486 w^2 + 9w - 486 = 0 w = 18 (throwing out neg(-27) solution for length w = 18 ft and length = 27 ft CHECKING our Answer*** 18*27 = 486 ```
 Exponential-and-logarithmic-functions/609969: Please help with this. "write the equation of the parabola in vertex form. V-Vertex, P-Point. V(0,0); P(1,7) Thank you for your help.1 solutions Answer 384051 by ewatrrr(10682)   on 2012-05-11 14:23:20 (Show Source): You can put this solution on YOUR website! ``` Hi, Using the vertex form of a parabola, where(h,k) is the vertex y = ax^2 7 = a(1)^2 7 = a ```
 Exponential-and-logarithmic-functions/609971: Please help with this. "write the equation of the parabola in vertex form. V-Vertex, P-Point." V(-2,4);P(3,-1) Thank you so much!!1 solutions Answer 384050 by ewatrrr(10682)   on 2012-05-11 14:14:45 (Show Source): You can put this solution on YOUR website! ``` Hi, Using the vertex form of a parabola, where(h,k) is the vertex V(-2,4);P(3,-1) x = a(y-4)^2 -2 3 = a(-5)^2 -2 5/25 = a 1/5 = a ,this is the Vertex form for parabola opening right and or left ( in this case >0, opens right. ```
 Coordinate-system/609961: Points (2,1) and (4,-7) are endpoints of the diameter of a circle. What is the length of the diameter, center of the circle and equation of the circle? Thanks and please show work. 1 solutions Answer 384045 by ewatrrr(10682)   on 2012-05-11 13:51:44 (Show Source): You can put this solution on YOUR website! ``` Hi, Points (2,1) and (4,-7) are endpoints of the diameter of a circle. D = r = Midpoint Pt(x,y): ( , ) Midpoint Pt (3,-3)is the Center of this circle ```
 Probability-and-statistics/609902: The amount of Jen's monthly phone bill is normally distributed with a mean of \$50 and a standard deviatin of \$10. What is the 25th percentile?1 solutions Answer 384039 by ewatrrr(10682)   on 2012-05-11 12:58:18 (Show Source): You can put this solution on YOUR website! ``` Hi, understand now You were referring to this Inquiry monthly phone bill is normally distributed with a mean of \$50 and a standard deviation of \$10 What is the 25th percentile: (x-50)/10 = -.6745 ||Note: NORMSINV(0.25)= -.6745 (x-50)/10 = -.6745 x = \$43.26 ```
 Probability-and-statistics/609909: 5. Jane has twelve stamps worth 25 cents each and eight stamps worth 13 cents each? She selects five stamps without looking. What is the probability that she takes three of the 25 cent stamps and two of the 13 cent stamps? 1 solutions Answer 384028 by ewatrrr(10682)   on 2012-05-11 12:14:06 (Show Source): You can put this solution on YOUR website! ``` Hi Jane has stamps: twelve stamps worth 25 cents each and eight stamps worth 13 cents each? Selects 5 P(3(25¢) and 2(13¢) = 12C3*8C2/20C5 = 220*28/15504 = .3973 ```
 Probability-and-statistics/609927: a basketball player makes 70% of the free throws he shoots. if he tries 13 throws what is the probability that he will make more than five throws?1 solutions Answer 384027 by ewatrrr(10682)   on 2012-05-11 12:05:40 (Show Source): You can put this solution on YOUR website! ``` Hi Note: The probability of x succesP(0)ses in n trials is: P = nCx* where p and q are the probabilities of success and failure respectively. In this case p= .70 & q = .30 and n = 13 nCx = P( making >5) = 1 - [P(0)+P(1)+ P(2) + P(3) + P(4)+ P(5)] P = 1-( ++++)= .9960 Recommend using TI or stattrek.com for statistical calculations. Above is an explanatory presenation. Hope this helps. ```
 Probability-and-statistics/609928: the lifetime of a battery is normally distributed with a mean life of 40 hours and a standard deviation of 1.2 hours. find the probability that a randomly selected battery lasts longer than 42 hours?1 solutions Answer 384026 by ewatrrr(10682)   on 2012-05-11 11:49:22 (Show Source): You can put this solution on YOUR website! ``` Hi 40 hours and a standard deviation of 1.2 hours P(lasts longer than 42 hours) = 1 -P(z ≤ (42-40)/1.2) = 1 -NORMSDIST(1.6667)= .0478 ```
 Probability-and-statistics/609930: an urn contains 5 yellow, 6 green and 7 blue balls. two balls are randomly drawn without replacement. find the probability of the following events: A. both balls are green B. the first ball is blue and the second is yellow C. there is one green and one yellow ball 1 solutions Answer 384025 by ewatrrr(10682)   on 2012-05-11 11:41:45 (Show Source): You can put this solution on YOUR website! ``` Hi urn contains balls: 5 yellow, 6 green and 7 blue balls two balls are randomly drawn 'without' replacement A. P(both balls are green) = B. P(the first ball is blue and the second is yellow) = C. P(there is one green and one yellow ball)= 6C1*5C1/18C2 = 30/153 = 10/51 ```
 Money_Word_Problems/609665: Suppose you earn a salary of \$24000 per year. About what salary would you need 4 years from now to maintain your purchasing power in case the inflation rate stays at 2.9%?1 solutions Answer 384024 by ewatrrr(10682)   on 2012-05-11 11:24:23 (Show Source): You can put this solution on YOUR website! ``` Hi salary of \$24000 per year. About what salary would you need 4 years from now to maintain your purchasing power in case the inflation rate stays at 2.9%? In General A = Accumulated Amount P= principal = \$22400 r= annual rate = .029 n= periods per year = 1 t= years = 1 A= = \$25,725 ```
 Money_Word_Problems/609921: 'What annual rate of interest would you have to earn on an investment of \$2500 to ensure receiving \$152.50 interest after 1 year?'1 solutions Answer 384023 by ewatrrr(10682)   on 2012-05-11 11:20:03 (Show Source): You can put this solution on YOUR website! ``` Hi, re TY, please post so as Inquiry is placed in proper section. TY. 'What annual rate of interest would you have to earn on an investment of \$2500 to ensure receiving \$152.50 interest after 1 year?' In General A = Accumulated Amount = \$2652.50 P= principal = \$2500 r= annual rate = n= periods per year = 1 t= years = 1 2650.50/2500 -1 = r r = .061 or 6.1% ```
 Money_Word_Problems/609924: What is the amount in an account after 5 years if \$6000 is invested at 4% annual interest if interest is compounded monthly?1 solutions Answer 384022 by ewatrrr(10682)   on 2012-05-11 11:14:29 (Show Source): You can put this solution on YOUR website! ``` Hi \$6000 is invested 5 years at 4% annual interest,compounded monthly In General A = Accumulated Amount P= principal = \$6000 r= annual rate = .04 n= periods per year = 12 t= years = 5 A = = \$7181.37 ```
 logarithm/609917: 1. Find the logarithm log7(343) 2. solve 2log 16(x)-6=-51 solutions Answer 384021 by ewatrrr(10682)   on 2012-05-11 10:48:33 (Show Source): You can put this solution on YOUR website! ``` Hi logarithm = 3, as 7^3 = 343 2log16(x)-6= -5 = 1/2 16^(1/2) = x = 4 ________________________________________________________________________ ```
 Probability-and-statistics/609807: You draw from bag 5 times, and there are 4 red and 6 black balls in the bag. what's the probability that 3 red will be drawn with no replacement?1 solutions Answer 384018 by ewatrrr(10682)   on 2012-05-11 10:13:26 (Show Source): You can put this solution on YOUR website! ``` Hi You draw from bag times that has 4 red and 6 black balls in it, with no replacement P(3 reds) = (4C3*6C2)/10C5 = 4*15/152 = 60/152 = 15/38 ```
 Probability-and-statistics/609808: Find the normal approximation for the binomial probability that x = 5, where n = 14 and p = 0.5. 1 solutions Answer 384017 by ewatrrr(10682)   on 2012-05-11 10:08:31 (Show Source): You can put this solution on YOUR website! ``` Hi Note: The probability of x successes in n trials is: P = nCx* where p and q are the probabilities of success and failure respectively. In this case p & q are = 1/2 or .5 nCx = 14C5 = 2002 P(5) =2002* = .1222 Can highly recommend stattrek.com for statistical calculations ```
 Probability-and-statistics/609895: (1) if light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviatin of 500 hurs, what percentage of light bulobs have a life less than 2500 hours? 1 solutions Answer 384016 by ewatrrr(10682)   on 2012-05-11 10:02:19 (Show Source): You can put this solution on YOUR website! ``` Hi Light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours what percentage of light bulbs have a life less than 2500 hours(the mean)? 50% ```
 Probability-and-statistics/609896: the lifetime of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has lifetimes that lie within 1 standard deviation of the mean on either side?1 solutions Answer 384015 by ewatrrr(10682)   on 2012-05-11 09:58:27 (Show Source): You can put this solution on YOUR website! ``` Hi, re TY, see higlighted Percentage (Others were for comparison purposes only) the lifetime of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has life times that lie within 1 standard deviation of the mean on either side? ****one standard deviation from the mean accounts for about % of the set two standard deviations from the mean account for about 95.4% and three standard deviations from the mean account for about 99.7%. ```