document.write( "Question 1201541: The average age of two sisters is three times the age of the younger one . in seven years' time the sum of their ages will be greater than the difference in their ages by 20 years. how old are they now? (The answer is 3 and 15)
\n" ); document.write( " so ,
\n" ); document.write( "Let x=older sister and y=younger sister
\n" ); document.write( "x+y=3y
\n" ); document.write( "7+(x+y) greater than (x-y)+20 \r
\n" ); document.write( "\n" ); document.write( "But how can you form Simultaneous equations from this ? How is it worked out ? \n" ); document.write( "
Algebra.Com's Answer #835973 by MathTherapy(10552)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "The average age of two sisters is three times the age of the younger one . in seven years' time the sum of their ages will be greater than the difference in their ages by 20 years. how old are they now? (The answer is 3 and 15)\r\n" );
document.write( " so , \r\n" );
document.write( "Let x=older sister   and y=younger sister \r\n" );
document.write( "x+y=3y\r\n" );
document.write( "7+(x+y) greater than (x-y)+20 \r\n" );
document.write( "\r\n" );
document.write( "But how can you form Simultaneous equations from this ? How is it worked out ?\r\n" );
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document.write( "You don't need simultaneous/Systems of equations for every problem, unless asked to form and/or use them.\r\n" );
document.write( "This is solved by simply using only 1 (ONE) variable. That's ALL that's needed!\r\n" );
document.write( "\r\n" );
document.write( "Let the younger's age be Y\r\n" );
document.write( "Since the average of the ages is thrice the younger's age, then the 2 ages' average is, 3Y, thus\r\n" );
document.write( "making the sum of their ages, 6Y, with the older's age being 5Y. \r\n" );
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document.write( "I hope you're following up to this point.\r\n" );
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document.write( "Now, in 7 years'time, the sum of their ages will be 6Y + 2(7) = 6Y + 14\r\n" );
document.write( "                                                 We then get: 6Y + 14 = (5Y - Y) + 20\r\n" );
document.write( "                                                              6Y + 14 = 4Y + 20\r\n" );
document.write( "                                                              6Y - 4Y = 20 - 14\r\n" );
document.write( "                                                                   2Y = 6\r\n" );
document.write( "                                                  Younger's age or \r\n" );
document.write( "As the older is 5 times the younger's age (5Y), the older is: 5(3) = 15 years-old
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