Three spheres of radius 6 cm, x cam and y cm are melted to form a sing

1.	Three spheres of radius 6 cm, x cam and y cm are melted to form a single sphere of radius 12 cm. If xy is equal to 80, then the value of x + y is 1. 21 2. 18 3. 24 4. 42
Answer» 2. 18 Given xy = 80 and 6³+ x³ + y³ = 123 ⇒ x³ + y³ = 1512 ⇒ (x + y)³ - 3xy (x+y) = 1512 Let x + y = a So, given equation reduces to a³ - 240a - 1512 = 0 Now, a = 18 is root of above equation ⇒ x + y = 18

Three spheres of radius 6 cm, x cam and y cm are melted to form a single sphere of radius 12 cm. If xy is equal to 80, then the value of x + y is 1. 21 2. 18 3. 24 4. 42

Answer»

2. 18

Given xy = 80 and 6³+ x³ + y³ = 123 ⇒ x³ + y³ = 1512

⇒ (x + y)³ - 3xy (x+y) = 1512

Let x + y = a

So, given equation reduces to a³ - 240a - 1512 = 0

Now, a = 18 is root of above equation ⇒ x + y = 18

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Three spheres of radius 6 cm, x cam and y cm are melted to form a single sphere of radius 12 cm. If xy is equal to 80, then the value of x + y is 1. 21 2. 18 3. 24 4. 42

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