The sum of two numbers a and b is 15, and the sum of their reciprocals is 3/10. Find the numbers a and b.
Let the numbers be ‘a’ and ‘b’
Given, sum of two numbers is 15. The sum of their reciprocals is 1/4
⇒ a + b = 15
⇒ b = 15 – a
Also, 1/a + 1/b = 3/10
⇒ 1/a + 1/(15 – a) = 3/10
⇒ 15 × 10 = 45a – 3a2
⇒ a2 – 15a + 50 = 0
⇒ a2 – 15a – 5a + 50 = 0
⇒ a(a – 10) – 5(a – 10) = 0
⇒ (a – 5)(a – 10) = 0
⇒ a = 5, 10
Numbers are are 5,10 or 10, 5