Solved Exercises on Counting by Hundreds in Grade 1

Master counting by hundreds: place value understanding, skip counting patterns, and number sequences through these 3 detailed exercises.

Solution: Exercises 1 to 3
1 Basic counting by hundreds
Exercise 1
Count by hundreds starting from 100 up to 1000.
Write the sequence: 100, 200, 300, ...
Definition:

Counting by hundreds: Adding 100 to each number to get the next number in the sequence

Counting method:
  1. Start with the first number (100)
  2. Add 100 to get the next number
  3. Continue adding 100 to each subsequent number
Starting Point
100
Pattern
+100
Sequence
100, 200, 300...
Step 1: Start with 100

100 is our first number in the sequence

Step 2: Add 100 to get the next number

100 + 100 = 200

Step 3: Continue the pattern

200 + 100 = 300, 300 + 100 = 400, and so on

100, 200, 300, 400, 500, 600, 700, 800, 900, 1000
Final answer:

The sequence is: 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000

Applied rules:

• Counting by hundreds: Add 100 to each number to get the next

• Place value: Only the hundreds digit changes, tens and ones stay the same

• Pattern recognition: Numbers increase by 100 each time

2 Counting backwards by hundreds
Exercise 2
Count backwards by hundreds starting from 1000 down to 100.
Write the sequence: 1000, 900, 800, ...
Definition:

Counting backwards by hundreds: Subtracting 100 from each number to get the next number in the sequence

Starting Point
1000
Pattern
-100
Sequence
1000, 900, 800...
Step 1: Start with 1000

1000 is our first number in the sequence

Step 2: Subtract 100 to get the next number

1000 - 100 = 900

Step 3: Continue the pattern

900 - 100 = 800, 800 - 100 = 700, and so on

1000, 900, 800, 700, 600, 500, 400, 300, 200, 100
Final answer:

The sequence is: 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100

Applied rules:

• Counting backwards by hundreds: Subtract 100 from each number to get the next

• Place value: Only the hundreds digit changes, tens and ones stay the same

• Pattern recognition: Numbers decrease by 100 each time

3 Finding missing numbers in hundreds sequence
Exercise 3
Fill in the missing numbers in this sequence:
200, 300, ___, 500, ___, 700
Definition:

Finding missing numbers: Identifying the pattern in a sequence and filling gaps by following the rule

Given Sequence
200, 300, ___, 500, ___, 700
Pattern
+100
Complete
200, 300, 400, 500, 600, 700
Step 1: Identify the pattern

From 200 to 300, we added 100. The pattern is counting by hundreds (+100)

Step 2: Apply the pattern to find the first missing number

300 + 100 = 400

Step 3: Apply the pattern to find the second missing number

500 + 100 = 600

Step 4: Verify the complete sequence

200, 300, 400, 500, 600, 700 - all numbers differ by 100

200, 300, 400, 500, 600, 700
Final answer:

The missing numbers are 400 and 600

Applied rules:

• Pattern recognition: Identify the consistent operation between consecutive numbers

• Consistency: Apply the same operation to find missing values

• Verification: Check that the completed sequence follows the same rule

Visual Infographic: Counting by Hundreds

Counting by Hundreds

Understanding Place Value and Number Patterns

100
200
300
400
500
600
700
800
900
1000
100
→
200
→
300
→
400
100
1 hundred
200
2 hundreds
300
3 hundreds
400
4 hundreds
Place Value
When counting by hundreds, only the hundreds digit changes. Tens and ones digits remain 0.
Pattern
Each number is 100 more than the previous number. The sequence increases by 100 each time.
Forward Counting
Add 100 to move forward: 100 → 200 → 300 → 400...
Backward Counting
Subtract 100 to move backward: 1000 → 900 → 800 → 700...
Rules and methods, laws,...
\(100 + 100 = 200\)
Basic Addition
Forward
\(n + 100\)
Adding hundreds
Backward
\(n - 100\)
Subtracting hundreds
Pattern
\(100, 200, 300...\)
Sequence rule
Place Value: In hundreds, the hundreds digit changes while tens and ones stay at 0.
Counting Rule: Each number in the sequence is exactly 100 more than the previous.
Key Concepts: Counting by Hundreds
\(n + 100\)
Counting Forward
Key definitions:

Counting by hundreds: A sequence where each number increases by 100 from the previous number

Hundreds place: The third digit from the right in a number, representing groups of 100

Number pattern: A predictable sequence following a specific mathematical rule

Complete methodology:
  1. Identify the starting number: Recognize the first number in the sequence
  2. Determine the operation: Decide whether to add 100 (forward) or subtract 100 (backward)
  3. Apply the pattern: Consistently add or subtract 100 to continue the sequence
  4. Verify the sequence: Check that each number differs from the previous by 100
Tip 1: Remember that counting by hundreds only changes the hundreds digit.
Tip 2: Use physical objects like base-ten blocks to visualize hundreds.
Tip 3: Practice counting aloud to build fluency with the sequence.
Tip 4: Look for the pattern: all hundreds end in 00 (100, 200, 300...).
Common errors: Forgetting to change only the hundreds digit, skipping numbers in sequence.
Practice tips: Start with smaller ranges (100-500), then extend to larger numbers.
Key rules to remember:

• Forward counting: Add 100 to each number to get the next

• Backward counting: Subtract 100 from each number to get the next

• Place value: Only the hundreds digit changes, tens and ones remain 0

• Pattern consistency: Every number in the sequence differs by 100

Questions & Answers

Question: Why do we count by hundreds? What's special about the number 100?

Answer: Counting by hundreds is important because 100 is a special number in our number system! It represents one group of ten tens (10×10=100). Our number system is based on tens, called the decimal system.

  • 100 helps us organize larger numbers easily
  • It makes counting faster when we have many objects
  • Money uses hundreds (100 cents = 1 dollar)
  • Measurements often use hundreds (centimeters in meters)

Think of 100 as a big bundle that contains 10 smaller bundles of 10. It's easier to count "one hundred, two hundred" than to count 1, 2, 3... all the way to 200!

Question: My child is having trouble recognizing the pattern when counting by hundreds. How can I help them see it better?

Answer: Here are effective strategies to help your child recognize the hundreds pattern:

  • Use visual aids like base-ten blocks - show how 10 tens make 1 hundred
  • Create a hundreds chart and color the numbers as you count
  • Point out that all hundreds end in "00": 100, 200, 300, etc.
  • Connect to real-life examples: $100 bills, pages in books, etc.

Try this activity: Have your child count by tens up to 100 (10, 20, 30...100), then explain that counting by hundreds is like doing that jump 10 times faster. The pattern becomes clearer when they understand the connection to tens.

Question: What happens if I start counting by hundreds from a number that's not a multiple of 100? Like 150?

Answer: Great question! You can start counting by hundreds from any number. If you start from 150:

150 → 250 → 350 → 450 → 550 → 650 → 750 → 850 → 950

Notice that the pattern still works - you're still adding 100 each time. The only difference is that you're not starting at a "round" hundred. The hundreds digit still increases by 1 each time (1→2→3→4...), but the tens and ones digits (50 in this case) stay the same.

This shows that counting by hundreds means increasing the hundreds place by 1, regardless of what the tens and ones digits are!