Question of The Day07-11-2022

If x, y and z are positive integers such that xy = 432, yz = 96 and z < 9, then the smallest possible value of x + y + z is

Answer

Correct Answer : c ) 46

Explanation :

In the given question,

it is given that:

x, y and z are integers and x > 0, y > 0, z > 0

xy = 432 ......(1)

yz = 96 ........(2)

z < 9

To find:

smallest value of x + y + z

Let us find the prime factorization of yz

yz = 96 = 2 x 2 x 2 x 2 x 2 x 3 = 25 x 31

it is given that z < 9

hence, the possible values of z can be 2, 3, 4, 6, 8 (as these numbers can be obtained from combinations from prime factorization of 96)

based on values of z as 2, 3, 4, 6, 8,

values of y respectively will be 48, 32, 24, 16, 12

Now based on values of y, we can find values of x from eq. 1

Values of x on the basis of values of y as 48, 32, 24, 16, 12, respectively will be:

9, 13.5, 18, 27, 36

As x is an integer so, x = 13.5 is not possible.

Now, we have four sets of values of x, y and z

Set 1:

x, y, z = 2, 48, 9

x + y + z = 59

Set 2:

x, y, z = 4, 24, 18

x + y + z = 46

Set 3:

x, y, z = 6, 16, 27

x + y + z = 49

Set 4:

x, y, z = 8, 12, 36

x + y + z = 56

The minimum value of x + y + z is 46

Hence, option (c) is the correct answer.

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