Q79 of 107 Page 104

My younger sister's age today is 3 times, what it will be 3 years from now minus 3 times what her age was 3 years ago. Find her present age.

Let the age of my younger sister be x yr.


Then, her age after 3 yr = (x + 3) yr.


Also, her age, 3 yr ago = (x – 3) yr.


It is given that her present age is 3 times her age after 3 yr minus 3 times her age 3 yr ago.


Therefore, the equation is x = 3(x + 3) – 3(x – 3)


⇒ x = 3x + 9 – 3x + 9


⇒ x = 18 yr.


Hence, her present age is 18 yr.


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