Question

The mean of X1X2 is six and mean of X1X2X3 is 7
find the value of X3

Answer 1

Answer:

Mean of Two numbers = Sum of terms / Number of terms

Let the terms be x₁ and x₂

=> Mean of two terms = x₁ + x₂ / 2

=> 6 = x₁ + x₂ / 2

=> x₁ + x₂ = 6 * 2 = 12   ...( 1 )

Now mean of three terms = Sum of terms / Number of terms

Now let the third term be x₃.

=> Mean of three terms = Sum of three terms / Number of terms

=> 7 = x₁ + x₂ + x₃ / 3

=> x₁ + x₂ + x₃ = 7 * 3 = 21

We already know the value of x₁ + x₂ from ( 1 ). Hence substituting the value we get,

=> 12 + x₃ = 21

=> x₃ = 21 - 12 = 9

Hence the value of x₃ is 9.