Salaries of Rida and Riya are in the ratio of 3: 5, respectively. If the salary of each one is increased by Rs. 5,000, then the new ratio becomes 5 : 7. What is Riya's present salary ?

Rs. 12,500

                            Rida : Riya 

Original salaries       3   :  5               

Increased salaries    5   :  7

                              ↓       ↓

                        +5000   +5000

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Using cross - multiplication, 

25R - 21R = (7 x 5000 - 5 x 5000)

⇒      4R    = 2 x 5000

⇒        R    = 2500

Riya's present salary = 5R = 5x 2500 = Rs. 12,500