[Fully_Updated]! Cisco 500-420 Exam Questions For Very Good Results

Subtraction (500-420)

• Subtraction of 500 - 420 involves finding the difference between these two numbers.
• The calculation can be broken down into parts to aid mental computation. (e.g., 500 – 400 = 100, then 100 – 20 = 80, then 80 – 0 = 80). This approach is particularly useful when working with numbers that fall into the hundreds or tens of hundreds.

Mental Math Strategies for Subtraction

• Decomposition: Breaking down one or both numbers into smaller, more manageable parts for calculation. For example, subtracting 38 from 56 can be done by subtracting 30 from 56 and then subtracting 8.
• Compensation: Adding or subtracting a small value to/from one of the numbers to make the subtraction easier, often to create a "friendly" number. For instance, to calculate 75 - 28, adjust the numbers so you can subtract 30 instead of 28. The procedure is usually to add to one of the numbers and take away from the other, with the final calculation resulting in the same result as the original expression.
• Front-end subtraction: Focus on the most significant digits first in a subtraction problem. An example would be using front-end subtraction to calculate 652 - 238 (600 - 200 + 50-30 + 2-8).
• Using known facts: Recognizing and leveraging known subtraction facts (like 10-5=5 or 12-7=5) to solve more complicated problems. For example, you can solve more complex subtraction problems with the smaller component by thinking about the known facts and mentally adding them to find the appropriate solution(s).

Number Line Concepts in Subtraction

• Number lines visualize numbers and their relationships.
• Subtraction on a number line represents moving to the left from a starting point. To subtract 32 from 60, start at 60, and move 32 units to the left on the number line. The result is the new location on the number line.
• Understanding the relationship between addition and subtraction using the number line -- the act of subtracting from one number is the same as finding the difference to the number you wish to subtract from that number, you are, in effect, performing an inverse operation.
• Appropriate numbers on different intervals can be highlighted or emphasized when dealing with number line problems.

Integer Operations

• Integers include zero, positive whole numbers, and negative whole numbers.
• Subtraction with integers: Applying subtraction rules to negative and positive numbers requires acknowledging that subtracting a negative number is the same as adding a positive number; subtracting a positive number is the same as adding a negative number. For instance, 13 – (-7) = 13 + 7, or -8 – 5 = -8 + (-5)
• Visualizing integers on a number line aids in comprehending subtractions with positive and negative numbers.
• The rules for subtraction with integers can sometimes be represented using concepts from algebra, as subtraction can be performed as addition of the opposite (additive inverse). Example: 5- (-2) = 5+2=7.
• The concept of zero pairs can be used to understand subtraction of integers by identifying and eliminating matching positive and negative integers to arrive at the desired final result. For instance, there's a zero pair in -2 + 2, which equals zero.
• Subtraction with integers can be further explained through examples where borrowing or carrying are involved. For example, (-7) - 2 can be thought of as (-7) + (-2) = -9.