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Question

Three distinct positive integers a, b and c are such that b $-$ a = c $-$ b and a + b + c = 12. What is the maximum number of such possible sets (a, b, c) ?

The correct answer is
3

To solve this problem, we need to find the number of sets \((a, b, c)\) of distinct positive integers that satisfy the conditions \(b - a = c - b\) and \(a + b + c = 12\).

First, let's express the condition \(b - a = c - b\).

From this, we can deduce: \(b - a = c - b \implies b - a = b - b + x \implies c = 2b - a\), where \(x\) is the common difference.

Now substitute this expression for \(c\) into the equation \(a + b + c = 12\):

\(a + b + (2b - a) = 12\)

Simplifying gives:

\(3b = 12 \implies b = 4\)

With \(b = 4\), substitute back to find \(a\) and \(c\):

\(a = 4 - x\\) and \(c = 4 + x\), ensuring distinct positive integers.

Substituting into \(a + b + c = 12\):

\((4 - x) + 4 + (4 + x) = 12\)

Simplifying confirms the equality for all values of \(x\) satisfying integer conditions.

Finding distinct positive integers for them, try \(a = 3, b = 4, c = 5\); \(a = 2, b = 4, c = 6\); and \(a = 1, b = 4, c = 7\):

Setabc
1345
2246
3147

Thus, there are 3 potential sets \((a, b, c)\) satisfying the conditions.

Therefore, the correct answer is 3.

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Important Questions from Number System

  1. What is the value of 1 2 + 2 2 + 3 2 + ......21 2 ?

  2. Which sequence is correct to represent the hierarchical chain of number system?

    (Where N - Natural Numbers

    W - Whole Numbers

    Q - Rational Numbers

    Z - Integers)

  3. What must be added to 45680 to make it exactly divisible by 9?

  4. How many zeroes are there at the end of the following product? 

    1 x 5 x 10 x 15 x 20 x 25 x 30 x 35 x 40 x 45 x 50 x 55 x 60

  5. Let XYZ be a three-digit number, where (x + y + Z) is not a multiple of 3. Then (XYZ + YZX + ZXY) is not divisible by

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