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Question

For integers a, b and c, what would be the minimum and maximum values respectively of a + b + c if log |a| + log |b| + log |c| = 0?

The correct answer is

-3 and 3

To determine the minimum and maximum values of a + b + c for integers a, b, c, given the logarithmic equation log |a| + log |b| + log |c| = 0, we will first simplify the given expression using logarithm properties.

Logarithm Equation Simplification

The sum of logarithms can be expressed as the logarithm of the product of their arguments. This is a fundamental property of logarithms:

$\log X + \log Y + \log Z = \log (XYZ)$

Applying this property to our given equation, log |a| + log |b| + log |c| = 0, we get:

$\log (|a| \cdot |b| \cdot |c|) = 0$

Absolute Product Derivation

Next, we utilize the property that if $\log M = 0$, then the argument $M$ must be equal to 1. This holds true for any valid logarithm base, as any non-zero number raised to the power of 0 equals 1.

From $\log (|a| \cdot |b| \cdot |c|) = 0$, we deduce:

$|a| \cdot |b| \cdot |c| = 1$

Integer Value Determination for a, b, c

We are given that a, b, c are integers. For the product of their absolute values ($|a|$, $|b|$, $|c|$) to be equal to 1, and since absolute values are non-negative, each individual absolute value must be 1. This is because 1 is the only positive integer whose only positive integer factor is itself.

Therefore, we must have:

  • $|a| = 1$
  • $|b| = 1$
  • $|c| = 1$

This implies that each integer a, b, c can only take one of two possible values:

  • $a = 1$ or $a = -1$
  • $b = 1$ or $b = -1$
  • $c = 1$ or $c = -1$

Maximum Value of a + b + c

To obtain the maximum possible value for the sum a + b + c, we should choose the largest possible value for each of the variables a, b, c. From our derivation, the largest possible integer value for each variable is 1.

  • Choose $a = 1$
  • Choose $b = 1$
  • Choose $c = 1$

The resulting maximum sum is:

$a + b + c = 1 + 1 + 1 = 3$

Minimum Value of a + b + c

Conversely, to find the minimum possible value for the sum a + b + c, we should select the smallest possible value for each of the variables a, b, c. From our derivation, the smallest possible integer value for each variable is -1.

  • Choose $a = -1$
  • Choose $b = -1$
  • Choose $c = -1$

The resulting minimum sum is:

$a + b + c = (-1) + (-1) + (-1) = -3$

Summary of Results

Based on these calculations, the minimum and maximum values of a + b + c are -3 and 3 respectively.

Value Type Integer Choices for a, b, c Resulting Sum (a + b + c)
Minimum Value $a = -1$, $b = -1$, $c = -1$ $-3$
Maximum Value $a = 1$, $b = 1$, $c = 1$ $3$

Therefore, the minimum value is -3 and the maximum value is 3.

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Important Questions from Numerical Computation

  1. A cube of side 3 units is formed using a set of smaller cubes of side 1 unit. Find the proportion of the number of faces of the smaller cubes visible to those which are NOT visible.

  2. What is the average of all multiples of 10 from 2 to 198?

  3. Ratio of the angles of a triangle are 1 : 2 : 6. What is the smallest angle?

  4. A deposit in a bank, which pays interest on its deposits compounded daily, grows to Rs. 80,000 for 500 days and to 88,000 for 1000 days. What would be its value (in Rs.) for 1500 days?

  5. Among A, B, C and D, there is a lawyer, a doctor, a teacher and a journalist. They drink exactly one each of tea, coffee, lemonade and milk. If neither the lawyer nor the teacher drinks milk, B drinks coffee, A is the teacher and C is the doctor and drinks tea, then which of the following is FALSE?

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