Math Problem Statement

A number, a, rounded to 1 d.p. is 49.3. Another number, b, rounded to 1 d.p. is 7.6. What are the lower and upper bounds of a - b?

Solution

Let’s solve this problem step by step.

Step 1: Understand the rounding

  • A number rounded to 1 decimal place (1 d.p.) could vary by ±0.05 from its rounded value.
    • For a=49.3a = 49.3, its true value lies in the range: 49.25a<49.3549.25 \leq a < 49.35
    • For b=7.6b = 7.6, its true value lies in the range: 7.55b<7.657.55 \leq b < 7.65

Step 2: Compute the bounds for aba - b

The difference aba - b will have the following:

  • Minimum value: When aa is at its lower bound (49.25) and bb is at its upper bound (7.65): Minimum (ab)=49.257.65=41.6\text{Minimum } (a - b) = 49.25 - 7.65 = 41.6
  • Maximum value: When aa is at its upper bound (49.35) and bb is at its lower bound (7.55): Maximum (ab)=49.357.55=41.8\text{Maximum } (a - b) = 49.35 - 7.55 = 41.8

Final Answer:

The lower and upper bounds of aba - b are: 41.6ab<41.841.6 \leq a - b < 41.8

Would you like further clarification or details on how to handle similar problems?


Related Questions:

  1. How are bounds affected when rounding to 2 decimal places instead of 1?
  2. Can aba - b ever equal exactly 41.7 in this scenario?
  3. How do we compute bounds for addition a+ba + b?
  4. What happens if both aa and bb are rounded to whole numbers instead?
  5. How does rounding impact calculations in practical scenarios?

Tip:

When dealing with bounds, always calculate extremes (minimum and maximum) by combining the smallest and largest possible values strategically.

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Math Problem Analysis

Mathematical Concepts

Rounding
Bounds
Subtraction

Formulas

Lower bound = Rounded value - 0.05
Upper bound = Rounded value + 0.05
Minimum difference = Lower bound of a - Upper bound of b
Maximum difference = Upper bound of a - Lower bound of b

Theorems

Properties of rounding and bounds

Suitable Grade Level

Grades 7-10