31. If the sum of two numbers is 10 and the sum of their reciprocals is 5/12 then what will be the numbers ?/ यदि दो संख्याओं का योग 10 है और उनके व्युत्क्रमों का योग 5/12 है तो संख्याएँ क्या होंगी?
7, 3
9, 1
8, 2
6, 4
Answer / उत्तर -6, 4
explanation / स्पष्टीकरण :-
Let the numbers be x and y
So, x + y = 10 ----(i)
And, (1/x) + (1/y) = 5/12 ----(ii)
⇒ (x + y)/xy = 5/12
Now,
⇒ 10/xy = 5/12
⇒ xy = 12 × 2 = 24 ----(iii)
Now, (10 – y) × y = 24
⇒ 10y – y = 24
⇒ y – 10y + 24 = 0
⇒ y – 6y – 4y + 24 = 0
⇒ y(y – 6) – 4(y – 6) = 0
⇒ (y – 6) (y – 4) = 0
⇒ y = 6, 4
∴ The required numbers are 6 and 4
explanation / स्पष्टीकरण :-
Let the numbers be x and y
So, x + y = 10 ----(i)
And, (1/x) + (1/y) = 5/12 ----(ii)
⇒ (x + y)/xy = 5/12
Now,
⇒ 10/xy = 5/12
⇒ xy = 12 × 2 = 24 ----(iii)
Now, (10 – y) × y = 24
⇒ 10y – y = 24
⇒ y – 10y + 24 = 0
⇒ y – 6y – 4y + 24 = 0
⇒ y(y – 6) – 4(y – 6) = 0
⇒ (y – 6) (y – 4) = 0
⇒ y = 6, 4
∴ The required numbers are 6 and 4
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