Question Details

If a,b,c and d are integers such that their sum is 46, then the minimum possible value of    (a − b)2 + (a −c)2 + (a − d)2 is

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Correct Answer :

2

Solution :

The correct answer is 2.

Let us solve this step-by-step to understand how to minimize the given expression under the given condition.

We are given four integers a, b, c, and d such that their sum is 46:
a+b+c+d=46

We want to find the minimum possible value of the expression:
S=(a-b)2+(a-c)2+(a-d)2

To make the sum of non-negative squared terms as small as possible, the values of a, b, c, and d must be chosen as close to each other as possible, with a specifically chosen to be close to the average of the four integers.

Let us calculate the average of the four integers:
Average=464=11.5

Since a, b, c, and d are required to be integers, we split 46 into four integers as close to 11.5 as possible. The closest integers to 11.5 are 11 and 12.

To get a sum of 46 using only 11 and 12, we can choose two 11s and two 12s:
11+11+12+12=46

Now, let us assign these values to a, b, c, and d to evaluate S:

If we set a=11, then the remaining integers b, c, and d must be 11, 12, and 12.
Substituting these values into the expression:
S=(11-11)2+(11-12)2+(11-12)2
S=02+(-1)2+(-1)2
S=0+1+1=2

Similarly, if we set a=12, the remaining integers are 11, 11, and 12:
S=(12-11)2+(12-11)2+(12-12)2
S=12+12+02=1+1+0=2

Thus, the minimum possible value of (a-b)2+(a-c)2+(a-d)2 is 2.

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