Solved Exercises on Counting by 10's to 1000 in Grade 2

Master counting by 10's to 1000: skip counting, place value understanding, and number sequence recognition through these 5 detailed exercises.

Solution: Exercises 1 to 3
1 Skip Counting by 10s
Exercise 1
Fill in the missing numbers in this pattern:
100, 110, 120, ___, 140, 150, ___
Definition:

Skip counting by 10s: Adding 10 to each number to get the next number in the sequence

Skip counting method:
  1. Identify the pattern (adding 10 each time)
  2. Add 10 to the previous number to find the next number
  3. Continue the pattern until the end
Pattern
100, 110, 120, ?, 140, 150, ?
Rule
Add 10
Solution
130, 160
Step 1: Identify the pattern

110 - 100 = 10, so we're adding 10 each time

Step 2: Find the first missing number

120 + 10 = 130

Step 3: Find the second missing number

150 + 10 = 160

100, 110, 120, 130, 140, 150, 160
Final answer:

The missing numbers are 130 and 160

Applied rules:

• Pattern Recognition: Identify the constant difference between consecutive numbers

• Place Value: Only the tens digit changes when skip counting by 10s

• Consistency: The same rule applies to all numbers in the sequence

2 Skip Counting by 10s Backwards
Exercise 2
Count backwards by 10s starting from 500:
500, 490, 480, ___, 460, 450, ___
Definition:

Skip counting by 10s backwards: Subtracting 10 from each number to get the next number in the sequence

Pattern
500, 490, 480, ?, 460, 450, ?
Rule
Subtract 10
Solution
470, 440
Step 1: Identify the pattern

500 - 490 = 10, so we're subtracting 10 each time

Step 2: Find the first missing number

480 - 10 = 470

Step 3: Find the second missing number

450 - 10 = 440

500, 490, 480, 470, 460, 450, 440
Final answer:

The missing numbers are 470 and 440

Applied rules:

• Backward Counting: Subtract the same amount each time

• Place Value: Only the tens digit changes when skip counting by 10s

• Consistency: The same operation applies to all numbers in the sequence

3 Skip Counting by 10s Across Hundreds
Exercise 3
Complete the sequence counting forward by 10s:
980, 990, 1000, 1010, 1020, 1030, ___
Definition:

Skip counting by 10s across hundreds: Adding 10 to numbers that cross hundreds boundaries

Pattern
980→990→1000→1010→1020→1030→?
Rule
Add 10
Solution
1040
Step 1: Identify the pattern

990 - 980 = 10, so we're adding 10 each time

Step 2: Recognize the transition point

From 990 to 1000, the tens digit changes from 9 to 0 and the hundreds digit increases

Step 3: Continue the pattern

1030 + 10 = 1040

Step 4: Verify the sequence

1040 - 1030 = 10 ✓, confirming our pattern

980, 990, 1000, 1010, 1020, 1030, 1040
Final answer:

The missing number is 1040

Applied rules:

• Pattern Recognition: Identify the constant difference (10) between consecutive numbers

• Place Value: Understand how digits change when crossing hundreds boundaries

• Verification: Check that the pattern holds between known numbers

Rules and methods, laws,...
Skip Counting: Start + Step × Position
Number Sequence Formula
Skip by 10s
Add 10
Pattern: 100, 110, 120, 130...
Skip by 10s
Subtract 10
Pattern: 500, 490, 480, 470...
Cross Hundreds
990→1000
Tens reset, hundreds increase
Key definitions:

Skip Counting: Counting by a number other than 1 (like 10s)

Place Value: Understanding hundreds, tens, and ones in 3-digit numbers

Number Pattern: A sequence of numbers that follows a specific rule

Transition Point: When counting reaches a boundary (like 99 to 100) and place values change

Complete methodology:
  1. Analyze the sequence: Look at the first few numbers to identify the pattern
  2. Determine the step: Calculate the difference between consecutive numbers
  3. Apply the rule: Use the identified pattern to fill in missing numbers
  4. Verify your answer: Check that the pattern continues consistently
Tip 1: When counting by 10s, only the tens digit changes (120, 130, 140).
Tip 2: When the tens digit is 9, the next number crosses to the next hundred (190→200).
Tip 3: When counting by 10s backwards, the tens digit decreases by 1 each time.
Tip 4: Use your fingers or count aloud to check your pattern.

Common errors: Forgetting to change the correct digit, miscounting the step, not recognizing the pattern.
Key notes: When tens digit is 9, adding 10 causes hundreds digit to increase.
Rules to know by heart:

• Skip by 10s: Add 10 each time (tens digit increases by 1)

• Skip by 10s backwards: Subtract 10 each time (tens digit decreases by 1)

• When tens digit is 9: Adding 10 increases hundreds digit (190→200)

• When tens digit is 0: Subtracting 10 decreases hundreds digit (200→190)

• Pattern consistency: The same rule applies throughout the sequence

Solution: Exercises 4 to 5
4 Skip Counting by 10s with Large Numbers
Exercise 4
Identify the pattern and continue the sequence:
750, 760, 770, 780, 790, 800, 810, ___
Definition:

Skip counting by 10s with large numbers: Continuing the pattern when crossing hundreds boundaries

Sequence
750→760→770→780→790→800→810→?
Pattern
Add 10
Next
820
Step 1: Analyze the differences

760-750=10, 770-760=10, 780-770=10, 790-780=10

Step 2: Notice the transition point

From 790 to 800, the tens digit changes from 9 to 0 and hundreds increase

Step 3: Apply the pattern

After 810, the next number is 810 + 10 = 820

Step 4: Calculate the next number

810 + 10 = 820

Next number: 820
Final answer:

The next number in the sequence is 820

Applied rules:

• Pattern Analysis: Calculate differences between consecutive numbers

• Transition Recognition: Identify when crossing hundreds boundaries

• Consistency Check: Verify the pattern continues correctly

5 Skip Counting by 10s to 1000
Exercise 5
Complete the sequence counting by 10s to 1000:
970, 980, 990, 1000, 1010, 1020, 1030, ___
Definition:

Place value transition: Understanding how numbers change when crossing hundreds boundaries

Sequence
970→980→990→1000→...→1030→?
Rule
Add 10
Result
1040
Step 1: Identify the pattern

Each number increases by 10 (980-970=10, 990-980=10, etc.)

Step 2: Understand place value transition

From 990 to 1000, the tens digit goes from 9 to 0, and the hundreds digit increases

Step 3: Calculate the next number

1030 + 10 = 1040

Step 4: Verify the pattern

1030 + 10 = 1040, maintaining the skip counting by 10s pattern

Next number: 1040
Final answer:

The next number in the sequence is 1040

Applied rules:

• Place Value Understanding: Know how digits change when reaching 9 in any place

• Hundreds Transition: When tens reach 90 and add 10, hundreds increase

• Pattern Consistency: Maintain the same skip counting rule throughout

Detailed Summary: Counting by 10's to 1000
nth Term = Start + (n-1) × 10
Arithmetic Sequence Formula
Key definitions:

Skip Counting by 10s: Counting forward or backward by a consistent interval of 10

Place Value: Understanding that each digit position represents hundreds, tens, or ones

Number Pattern: A sequence of numbers that follows a predictable rule

Transition Point: When counting reaches a boundary (like 99 to 100) and place values change

Complete methodology:
  1. Observe the sequence: Look at the first few numbers to understand the starting point
  2. Calculate differences: Find the difference between consecutive numbers to determine the step
  3. Identify the pattern: Determine if it's skip counting by 10s
  4. Apply the rule: Use the identified step to continue the sequence
  5. Verify results: Check that the pattern continues consistently throughout
Tip 1: When skip counting by 10s, the last digit stays the same while the tens digit changes.
Tip 2: When the tens digit is 9, adding 10 increases the hundreds digit (190→200).
Tip 3: Use your hands to count by 10s: 10, 20, 30, 40, etc. (each finger represents 10).
Tip 4: Practice counting forward and backward to strengthen number sense.
Common errors: Forgetting to carry over when reaching 9 in any place value, misidentifying the pattern, not maintaining consistency in the skip counting step.
Memory aids: Remember that skip counting by 10s changes only the tens digit (except at transition points).
Formulas to know by heart:

• Skip counting by 10s: Add 10 each time (100, 110, 120, 130...)

• Skip counting by 10s backwards: Subtract 10 each time (500, 490, 480, 470...)

• Transition rule: When tens digit is 9, adding 10 increases hundreds digit (190→200)

• Transition rule: When tens digit is 0, subtracting 10 decreases hundreds digit (200→190)

• Pattern consistency: The same rule applies throughout the sequence

Exercise with Visualization: Skip Counting by 10s to 1000
Exercise 6: Number Line Visualization
Visualize skip counting patterns on a number line:
Skip by 10s: 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200
Skip by 10s: 900, 910, 920, 930, 940, 950, 960, 970, 980, 990, 1000
100
110
120
130
140
150
160
170
180
190
200

Analysis: The visualization shows how skip counting creates evenly spaced intervals on the number line.

  • Skip by 10s: Consistent 10-unit jumps throughout the sequence
  • Transition point: At 190→200, the pattern continues smoothly
  • Pattern consistency: Equal distances between consecutive numbers

Questions & Answers

Question: I don't understand why when I count from 190 by 10s, it goes 190, 200, 210. Why does the 90 become 00?

Answer: Great question! This happens because of place value rules:

  • In 190, the tens digit is 9 and the ones digit is 0
  • When you add 10 to 190, you're adding to the tens place: 9 tens + 1 ten = 10 tens
  • But 10 tens equals 1 hundred, so you carry the 1 to the hundreds place
  • This makes the tens digit go back to 0, and the hundreds digit increases from 1 to 2
  • The ones digit stays the same (0)

So: 190 + 10 = 200 (1 hundred, 9 tens, 0 ones becomes 2 hundreds, 0 tens, 0 ones)

Think of it like having 99 cents and adding 10 cents - you now have $1.09, not 19009 cents!

Question: How can I remember whether to add or subtract when skip counting?

Answer: Here are some helpful strategies to remember:

  • Forward counting: Going up (like climbing stairs) means adding
  • Backward counting: Going down (like going down stairs) means subtracting
  • Look for direction words: "forward," "up," "more" usually mean addition
  • Look for direction words: "backward," "down," "less" usually mean subtraction

For example: "Count forward by 10s" means add 10 each time. "Count backward by 10s" means subtract 10 each time.

Tip: Practice with a number line - moving right is adding, moving left is subtracting!

Question: What's the easiest way to learn skip counting by 10s? I keep getting confused.

Answer: Here are effective strategies for skip counting by 10s:

  • Use your hands: Count your fingers - each hand has 5 fingers, so 2 hands = 10, 4 hands = 20, etc.
  • Notice the pattern: The ones digit stays the same (usually 0), only the tens digit changes
  • Connect to money: Dimes are worth 10 cents, so count dimes: 10¢, 20¢, 30¢, 40¢...
  • Count in groups: Think of sets of 10: 1 set = 10, 2 sets = 20, 3 sets = 30, etc.

Practice saying: "100, 110, 120, 130, 140, 150..." rhythmically. The rhythm helps your brain remember the pattern!

Start with smaller ranges (like 100-200) before attempting larger ranges (like 100-1000).