Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Place Value Identification: Determine which digit is in the position you are rounding to (the 'target digit').
The Neighbor Rule: Look at the digit immediately to the right of the target digit.
Round Up: If the neighbor digit is 5, 6, 7, 8, or 9, add 1 to the target digit.
Round Down (Stay the Same): If the neighbor digit is 0, 1, 2, 3, or 4, the target digit remains unchanged.
Zeroing Out: All digits to the right of the target digit must be replaced with zeros.
Rounding at the Boundary: When rounding a 9 up, it becomes 0 and increases the digit to its left by 1 (carrying over).
📐Formulae
💡Examples
Problem 1:
Round 4,562 to the nearest 10.
Solution:
4,560
Explanation:
The target digit is 6 (tens place). The neighbor digit is 2. Since 2 is less than 5, we keep the 6 the same and change the 2 to a 0.
Problem 2:
Round 7,384 to the nearest 100.
Solution:
7,400
Explanation:
The target digit is 3 (hundreds place). The neighbor digit is 8. Since 8 is 5 or more, we add 1 to the 3 to make it 4, and change all digits to the right to 0.
Problem 3:
Round 12,500 to the nearest 1,000.
Solution:
13,000
Explanation:
The target digit is 2 (thousands place). The neighbor digit is 5. According to the rule '5 or more', we round up. Add 1 to the 2 to make it 3, and replace the following digits with zeros.
Problem 4:
Round 84,999 to the nearest 10,000.
Solution:
80,000
Explanation:
The target digit is 8 (ten-thousands place). The neighbor digit is 4. Since 4 is less than 5, the 8 stays the same and all digits to the right become 0.
Problem 5:
Round 39,950 to the nearest 1,000.
Solution:
40,000
Explanation:
The target digit is 9 (thousands place). The neighbor is 9, so we round up. 9 + 1 becomes 10; we write 0 in the thousands place and carry 1 over to the ten-thousands place (3 + 1 = 4).