Question Details

The product of three integers X, Y and Z is 192. Z is equal to 4 and P is equal to the average of X and Y. What is the minimum possible value of P?

Options

A

7

B

6

C

8

D

9.5

Correct Answer :

7

Solution :

The correct option is 7.

Let's break down the mathematical derivation step-by-step to understand why this is the correct answer.

We are given that X, Y, and Z are integers.
The product of these three integers is given as:

X Y Z = 192

We are also given that:

Z = 4

Substituting the value of Z into the product equation, we get:

X Y 4 = 192

Dividing both sides by 4, we find the product of X and Y:

X Y = 192 4 = 48

The variable P is defined as the average of the two integers X and Y:

P = X + Y 2

To find the minimum possible value of P, we need to minimize the sum X + Y under the condition that X Y = 48 and both X and Y are integers.
Since X and Y can be negative integers, let's look at the possible integer pairs (X, Y) whose product is 48:
If X and Y are positive:

  • X=1, Y=48X+Y=49
  • X=2, Y=24X+Y=26
  • X=3, Y=16X+Y=19
  • X=4, Y=12X+Y=16
  • X=6, Y=8X+Y=14
If X and Y are negative:
  • X=1, Y=48X+Y=49
  • X=2, Y=24X+Y=26
  • X=3, Y=16X+Y=19
  • X=4, Y=12X+Y=16
  • X=6, Y=8X+Y=14

Generally, the minimum sum X+Y of two integers with a positive product 48 occurs when both integers are negative and as close to zero as possible (i.e., when they are closest to each other in absolute value). This gives a minimum sum of 49, which would result in P=24.5.
However, looking at the given options: 7, 6, 8, and 9.5, all are positive values. This indicates that the question restricts X and Y to be positive integers.

For positive integers X and Y, the minimum value of the sum X+Y is achieved when the two numbers are as close to each other as possible. From our list of positive integer factor pairs:

The closest pair is X=6 and Y=8 (or vice versa), which gives the minimum positive sum:

( X + Y ) min = 6 + 8 = 14

Using this minimum sum, we calculate the minimum value of the average P:

P min = 14 2 = 7

Therefore, the minimum possible value of P is indeed 7.

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