text: Question 48
  
  # The present age of Bob is equal to Abby’s age 8 years ago. Four years hence, the respective ratio between Bob’s age and Abby’s age will be 4 : 5 at that time. What is Bob’s present age?
  
  Solution
  
  Let the present ages of Abby be 'a' and Bob be 'b'
  b = a - 8 ---> (1)
  $$\frac{b+4}{a+4} = \frac{4}{5}$$
  5b + 4 = 4a
  5 (a - 8) + 4 = 4a
  a = 36
  b = 28
  Hence, the present age of Bob = 28 years
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