document.write( "Question 1197111: abbie paints twice as fast as beth and three times as fast as cathie. if it takes them 60 minutes to paint a living room with all three working together,how long would it take each woman working alone? \n" ); document.write( "
Algebra.Com's Answer #830228 by math_tutor2020(3817)![]() ![]() ![]() You can put this solution on YOUR website! \n" ); document.write( "Abbie paints twice as fast as Beth \n" ); document.write( "This means Beth takes twice as long as Abbie\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Abbie paints three times as fast as Cathie \n" ); document.write( "So Cathie takes three times as long as Abbie\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x = amount of time, in minutes, Abbie needs to do the job by herself \n" ); document.write( "2x = amount of time, in minutes, Beth needs to do the job by herself \n" ); document.write( "3x = amount of time, in minutes, Cathie needs to do the job by herself\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The reciprocal of each item represents the unit rate \n" ); document.write( "1/x = unit rate for Abbie \n" ); document.write( "1/(2x) = unit rate for Beth \n" ); document.write( "1/(3x) = unit rate for Cathie \n" ); document.write( "Each unit rate is in \"jobs per minute\". \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Those fractional unit rates add to this \n" ); document.write( "(1/x) + (1/(2x)) + (1/(3x)) \n" ); document.write( "(6/(6x)) + (3/(6x)) + (2/(6x)) \n" ); document.write( "(6+3+2)/(6x) \n" ); document.write( "11/(6x)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "If the girls work together, without getting in each others' way, then their combined unit rate is 11/(6x) jobs per minute.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Multiply this unit rate with the total time they use (60 min) and set this equal to 1 to represent getting 1 full job done.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So, \n" ); document.write( "(unit rate)*(time) = amount done \n" ); document.write( "(11/(6x))*(60 min) = 1 full job \n" ); document.write( "(11/(6x))*(60) = 1 \n" ); document.write( "110/x = 1 \n" ); document.write( "110 = x*1 \n" ); document.write( "x = 110\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Abbie needs 110 minutes to get the job done on her own. \n" ); document.write( "Beth needs 2x = 2*110 = 220 minutes to get the job done on her own. \n" ); document.write( "Cathie needs 3x = 3*110 = 330 minutes to get the job done on her own.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "===========================================================================================\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Another approach:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "a = Abbie's rate \n" ); document.write( "b = Beth's rate \n" ); document.write( "c = Cathie's rate\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Abbie paints twice as fast as Beth, so, \n" ); document.write( "a = 2b \n" ); document.write( "Also, Abbie paints three times as fast as Cathie \n" ); document.write( "a = 3c\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Both equations mentioned are equal to 'a', which means we can equate the right hand sides \n" ); document.write( "2b = 3c \n" ); document.write( "Divide both sides by 2 allowing us to solve for b \n" ); document.write( "b = 3c/2 = 1.5c\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So we can say \n" ); document.write( "a = 3c \n" ); document.write( "b = 1.5c\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The ratio a:b:c can be expressed as 3c:1.5c:c \n" ); document.write( "Multiply all parts by 2 to get 6c:3c:2c \n" ); document.write( "Every part of this ratio involves the variable c in some fashion.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The coefficients add to 6+3+2 = 11 \n" ); document.write( "We can think of it like saying
\n" ); document.write( "Let's say the job is to paint 3300 square feet of wall \n" ); document.write( "I picked some large multiple of 11. Feel free to pick something else. \n" ); document.write( "I picked a multiple of 11 so that multiplying with the fractions leads to a whole number.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Let's now subdivide the work like so
\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Since it took 60 minutes for each woman to do their portions of the wall, this means
\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Now let's have them work alone. \n" ); document.write( "If Abbie works alone, then she needs to paint the entire 3300 sq ft. Her unit rate is 30 sq ft per min. \n" ); document.write( "Therefore, she needs 3300/30 = 110 minutes. \n" ); document.write( "I'm using the idea that \n" ); document.write( "time = (amount done)/(rate of work)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "If Beth works alone, then she needs 3300/15 = 220 minutes\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "If Cathie works alone, then she needs 3300/10 = 330 minutes\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "===========================================================================================\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Answers: \n" ); document.write( "Abbie needs 110 minutes if she works alone \n" ); document.write( "Beth needs 220 minutes if she works alone \n" ); document.write( "Cathie needs 330 minutes if she works alone\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Footnotes: \n" ); document.write( "110 min = 60 min + 50 min = 1 hr + 50 min \n" ); document.write( "220 min = 180 min + 40 min = 3 hr + 40 min \n" ); document.write( "330 min = 300 min + 30 min = 5 hr + 30 min \n" ); document.write( "180 min = 180/60 = 3 hrs \n" ); document.write( "300 min = 300/60 = 5 hrs \n" ); document.write( " \n" ); document.write( " |