Question

the average of three numbers is -4 a new number is added to the list making the average -3 what is the new number?
please!! show me working out

Answer 1

Answer:

Let the three numbers be a, b and c & their average is - 4 given accordingly.

• According to the Question :

⇒ Average = Sum/Number

⇒ Average × Number = Sum

⇒ ( - 4) × 3 = (a + b + c)

⇒ (a + b + c) = - 12 ⠀⠀⠀— eq. ( I )

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A new number is added to list and average becomes - 3, let's say New number is d.

• We have again :

⇒ Average = Sum/Number

⇒ Average × Number = Sum

⇒ ( - 3) × 4 = (a + b + c + d)

⇒ - 12 = (a + b + c + d)

• Putting the value from eq. ( I )

⇒ - 12 = - 12 + d

⇒ - 12 + 12 = d

⇒ d = 0

∴ Hence, new number added in list is 0.