Question

Mary is twice older than her sister. In 5 years time, she will be 2 years older than her sister. find how old are they both now.

Answer 1

Heya !!




Let present age of Mary sister be X years.





Present age of Mary = 2X years.





After 5 years age of Mary = ( 2X + 5 ) years.



After 5 years age of her sister = ( X + 5 ) years




According to the question,


Age of Mary after 5 years = Age of Mary sister after 5 years + 2




2X + 5 = X + 5 + 2





2X - X = 7 - 5





X = 2



Present age of her sister = X = 2 years.



And,


Present age of Mary = 2X = 2 × 2 = 4 years.

Answer 2

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$let \: mary \: age \: = x \\ let \: her \: sister \: age \: = y \\ according \: to \: question \\ x = 2(y) - - - - - - 1 \\ after \: five \: years \: their \: age \: will \: be \\ mry \: age \: = x + 5 \\ her \: sister \: age \: = y + 5 \\ according \: to \: question \\ x +5= y + 5 + 2 \\ x-y=2 - - - - - 2 \\ from \: equation \: 1 \: and \: 2 \\ x - 2y = 0 \\ x - y = 2 \\ by \: elimimation \: method \\ - y = -2\\ minus \: minus \: cancelled \: then \\ y = 2\\ from \: 1 \: equation \: \\ x = 2y \\ x = 2 \times 2 \\ x = 4 \: answer$
so mary age is 4 years and her sister age is 2 years......


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