document.write( "Question 952520: 20 years ago Grandma was twice as old as Mum. Today, Grandma is twice the age Mum was when I was born. How old am I? \n" ); document.write( "

Algebra.Com's Answer #854444 by MathTherapy(10839) $\"\"$ $\"About$

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document.write( "20 years ago Grandma was twice as old as Mum. Today, Grandma is twice the age Mum was when I was born. How old am I?\r\n" );
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document.write( "Let Grandma's current age, be G, and Mum's, M\r\n" );
document.write( "Then 20 years ago Grandma was G - 20, and Mum was M - 20\r\n" );
document.write( "Given that, \"20 years ago Grandma was twice as old as Mum,\" gives us:\r\n" );
document.write( "G - 20 = 2(M - 20) ===> G - 20 = 2M - 40 ===> G = 2M - 40 + 20 ===> G = 2M - 20 ---- eq (i)\r\n" );
document.write( "G - 20 = 2(M - 20) ===> G - 20 = 2M - 40____G - 20 + 40 = 2M ===> G + 20 = 2M ====>  ----- eq (ii)\r\n" );
document.write( "Let the number of years since my birth, be y\r\n" );
document.write( "Mum's age, when I ws born: M - y, or \r\n" );
document.write( "\"Today, Grandma is twice the age Mum was when I was born,\" gives us: G = 2(M - y)\r\n" );
document.write( "                                                                                                                             ----- Substituting  for M\r\n" );
document.write( "                                                                                                                            G = G + 20 - 2y\r\n" );
document.write( "                                                                                                              G - G - 20 = - 2y ---- Subtracting 20 from each side\r\n" );
document.write( "                                                                                                                        - 20 = - 2y\r\n" );
document.write( "                                                                Years since I was born/my age, or

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