What is Rounding?

Rounding means adjusting a number to make it simpler while keeping its value close to the original. We round numbers when we don’t need exact precision – like estimating costs, telling time, or measuring distances.

Why Round Numbers?

• Makes calculations easier
• Helps with quick estimations
• Simplifies real-world measurements
• Useful for reporting approximate values

Rounding Rules Explained

1. Rounding to the Nearest Ten

Step-by-Step Process:

1. Locate the ones place (last digit)
2. Check the ones digit:
   • If it’s 5-9, round the tens place up
   • If it’s 0-4, keep the tens place same
3. Change ones digit to 0

Examples:

• 36 → 40 (6 in ones place → round up)
• 52 → 50 (2 in ones place → round down)
• 145 → 150 (5 in ones place → round up)

• Round 67 to the nearest ten.
  Look at the ones place: 7 (which is 5 or more).
  Round up the tens place from 6 to 7.
  So, 67 rounds to 70.
• Round 32 to the nearest ten.
  Look at the ones place: 2 (which is 4 or less).
  Keep the tens place the same: 3.
  So, 32 rounds to 30.

Visual Guide:

Numbers 31-34 → Round DOWN to 30
Numbers 35-39 → Round UP to 40

2. Rounding to the Nearest Hundred

Step-by-Step Process:

1. Locate the tens place (middle digit in 3-digit numbers)
2. Check the tens digit:
   • If it’s 5-9, round the hundreds place up
   • If it’s 0-4, keep the hundreds place same
3. Change tens and ones digits to 0

Examples:

• 327 → 300 (2 in tens place → round down)
• 485 → 500 (8 in tens place → round up)
• 1,450 → 1,500 (5 in tens place → round up)

• Round 438 to the nearest hundred.
  Look at the tens place: 3 (which is 4 or less).
  Keep the hundreds place the same: 4.
  So, 438 rounds to 400.
• Round 765 to the nearest hundred.
  Look at the tens place: 6 (which is 5 or more).
  Round up the hundreds place from 7 to 8.
  So, 765 rounds to 800.

Number Line Visualization:

400-449 → Round DOWN to 400
450-499 → Round UP to 500

Special Cases in Rounding

Rounding Numbers Ending in 5

• When a number ends with exactly 5 (e.g., 25, 135, 475):
• Common practice: Always round up
• Example: 75 → 80 (not 70)

Rounding Large Numbers

Same rules apply to thousands, millions, etc.:

• 4,782 → 5,000 (7 in hundreds place → round up thousands)
• 19,500 → 20,000 (5 in thousands place → round up ten-thousands)

Real-World Applications

Money & Shopping

• 3.78→”About3.78→”About4″
• 19.95→”Around19.95→”Around20″

Time Estimation

• 8:47 → “About 8:45” or “Nearly 8:50”
• 2 hours 38 minutes → “Approximately 2½ hours”

Measurement

• 247 cm → “About 250 cm”
• 1,982 grams → “Around 2 kilograms”

Rounding helps make numbers friendlier while keeping them useful. With these rules, you’ll be rounding like a pro in no time!