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

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

Solution: Exercises 1 to 3
1 Skip counting pattern
Exercise 1
Count by 10s starting from 100. Write the next 10 numbers in the sequence.
Definition:

Skip counting by 10s: Adding 10 to each number in a sequence

Skip counting method:
  1. Start with the given number
  2. Add 10 to get the next number
  3. Only the tens digit changes (usually)
  4. Repeat for the desired number of terms
Starting number
100
Add 10
100+10=110
Step 1: Start with 100

100 is our starting point (1 hundred, 0 tens, 0 ones)

Step 2: Add 10 to get next number

100 + 10 = 110 (1 hundred, 1 ten, 0 ones)

Step 3: Continue adding 10

110 + 10 = 120, 120 + 10 = 130, 130 + 10 = 140, 140 + 10 = 150, 150 + 10 = 160, 160 + 10 = 170, 170 + 10 = 180, 180 + 10 = 190, 190 + 10 = 200

100
110
120
130
140
150
160
170
180
190
100
→
110
→
120
→
130
→
140
→
150
→
160
→
170
→
180
→
190
→
200
100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200
Final answer:

The next 10 numbers are: 110, 120, 130, 140, 150, 160, 170, 180, 190, 200

Applied rules:

• Place value rule: Usually only the tens digit changes when counting by 10s

• Pattern recognition: Ones digit stays 0, tens digit increases by 1

• Exception: When tens digit is 9, it changes to 0 and hundreds digit increases

2 Missing number in sequence
Exercise 2
Find the missing number in this sequence: 230, 240, 250, ___, 270, 280
Definition:

Number sequence: A series of numbers following a specific pattern

Sequence
230, 240, 250, ?, 270, 280
Pattern
+10 each time
Missing
260
Step 1: Identify the pattern

240 - 230 = 10, 250 - 240 = 10

The pattern is adding 10 each time

Step 2: Apply the pattern

After 250: 250 + 10 = 260

Step 3: Verify with next number

260 + 10 = 270 ✓

230
240
250
260
270
280
230, 240, 250, 260, 270, 280
Final answer:

The missing number is 260

Applied rules:

• Pattern recognition: Identify consistent increments of 10

• Verification: Check that the pattern continues after the missing number

• Place value understanding: Only tens digit changes normally

3 Place value analysis
Exercise 3
What happens to the hundreds, tens, and ones digits when you count by 10s starting from 190?
Definition:

Place value: The value of each digit based on its position

Hundreds
1
Tens
9→0
Ones
0
Start
190
Add 10
190+10=200
Result
200
Step 1: Analyze 190

Hundreds: 1, Tens: 9, Ones: 0

Step 2: Add 10 to 190

190 + 10 = 200

Step 3: Analyze 200

Hundreds: 2, Tens: 0, Ones: 0

Step 4: Compare digits

Hundreds increased by 1 (1→2), Tens changed from 9 to 0, Ones stayed 0

190
→
200
190 → 200: H+1, T:9→0, O:0
Final answer:

When counting by 10s from 190 to 200:
- Hundreds digit increases by 1 (1→2)
- Tens digit changes from 9 to 0
- Ones digit remains 0

Applied rules:

• Carry over rule: When tens reach 10, carry 1 to hundreds

• Place value system: Each position represents powers of 10

• Regrouping: 10 tens = 1 hundred

Comprehensive Guide: Counting to 1000 by 10s
\(n + 10 = n + 10\)
Skip Counting by 10s
Key definitions:

Skip counting: Counting by a number other than 1 (counting by 2s, 5s, 10s, 100s, etc.)

Place value: The value of a digit based on its position in a number (hundreds, tens, ones)

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

Base-10 system: Our number system based on powers of 10

Complete methodology:
  1. Analyze the starting number: Identify hundreds, tens, and ones digits
  2. Apply the increment: Add or subtract 10 to the number
  3. Handle place value changes: Watch for when tens digit reaches 9 or 0
  4. Continue the pattern: Repeat the process for desired number of terms
  5. Verify the result: Check that the pattern is consistent
Tip 1: The ones digit usually stays the same when counting by 10s.
Tip 2: When the tens digit is 9, adding 10 increases the hundreds digit.
Tip 3: Practice with number lines to visualize the pattern.
Tip 4: Count by 10s from different starting points.
Tip 5: Skip counting by 10s helps prepare for multiplication.
Pattern characteristics: Consistent increment of 10, ones digit usually unchanged, tens digit increases by 1 (with exceptions).
Place value rules: When tens digit is 9, it resets to 0 and hundreds digit increases by 1.
Essential rules for counting by 10s:

• Ones digit: Usually remains the same

• Tens digit: Increases by 1 each time (except when it's 9)

• Hundreds digit: Increases by 1 when tens goes from 9 to 0

• Pattern consistency: Always add or subtract 10

• Carry/borrow rule: 10 tens = 1 hundred

\(n, n+10, n+20, n+30...\)
General Pattern Formula
Solution: Exercises 4 to 5
4 Counting backwards by 10s
Exercise 4
Count backwards by 10s starting from 300. Write the next 6 numbers.
Definition:

Backwards skip counting: Subtracting 10 from each number in a sequence

Start
300
Subtract 10
300-10=290
Next
290
Step 1: Start with 300

300 is our starting point (3 hundreds, 0 tens, 0 ones)

Step 2: Subtract 10 to get next number

300 - 10 = 290 (2 hundreds, 9 tens, 0 ones)

Step 3: Continue subtracting 10

290 - 10 = 280, 280 - 10 = 270, 270 - 10 = 260, 260 - 10 = 250, 250 - 10 = 240

300
290
280
270
260
250
240
300
→
290
→
280
→
270
→
260
→
250
→
240
300, 290, 280, 270, 260, 250, 240
Final answer:

The next 6 numbers are: 290, 280, 270, 260, 250, 240

Applied rules:

• Reverse pattern: Subtract 10 instead of adding

• Place value rule: Only tens digit changes (decreases by 1)

• Borrowing: When tens digit is 0, decrease hundreds digit

5 Word problem application
Exercise 5
A school has 150 students in the morning. Every 10 minutes, 10 more students arrive. How many students are there after 50 minutes?
Definition:

Word problem: Real-world scenario requiring mathematical solution

Initial
150
Minutes ÷ 10
50÷10=5
Additions
5×10=50
Total
150+50=200
Step 1: Identify initial amount

The school starts with 150 students

Step 2: Calculate number of 10-minute intervals

Every 10 minutes, 10 students arrive. In 50 minutes: 50 ÷ 10 = 5 intervals

Step 3: Calculate total addition

10 students arrive each interval for 5 intervals: 10 × 5 = 50 students

Step 4: Add to initial amount

150 + 50 = 200 students

Step 5: Verify with skip counting

150 → 160 → 170 → 180 → 190 → 200 (5 steps of 10)

150
160
170
180
190
200
150
→
160
→
170
→
180
→
190
→
200
150 + 50 = 200 students
Final answer:

There are 200 students after 50 minutes

Applied rules:

• Real-world application: Connect math to practical scenarios

• Problem solving: Break down word problems into steps

• Verification: Use multiple methods to confirm answer

Questions & Answers

Question: Why does the tens digit sometimes change from 9 to 0 when we count by 10s? It seems like it should just go 9→10.

Answer: Great observation! This happens because of how our number system works:

  • Our number system only uses digits 0-9 in each place
  • When we have 9 tens and add 1 more ten, we now have 10 tens
  • But we can't write "10" in the tens place, so we regroup: 10 tens = 1 hundred
  • This is why 190 + 10 = 200: we go from 1 hundred 9 tens to 2 hundreds 0 tens

Think of it like having 9 dimes. When you get 1 more dime, you now have 10 dimes, which equals 1 dollar. So you exchange 10 dimes for 1 dollar bill.

This is called "regrouping" and it's a fundamental part of our base-10 number system.

Question: How can I help my students understand that counting by 10s is different from regular counting?

Answer: Here are effective strategies:

  • Use concrete examples: Show with base-10 blocks how counting by 10s adds whole tens
  • Visual patterns: Use number grids to highlight the vertical pattern when counting by 10s
  • Compare and contrast: Show regular counting (1, 2, 3...) vs skip counting (10, 20, 30...)
  • Physical movement: Have students take 10 steps while counting by 10s

The key is helping students see that skip counting by 10s creates a predictable pattern where only certain digits change systematically.

Question: My child is confused about counting backwards by 10s. What's the best way to teach this?

Answer: Backwards counting can be challenging! Try these approaches:

  • Start with smaller numbers: Practice 100, 90, 80 before going to larger numbers
  • Use real-life contexts: Elevator scenarios (going down floors) or countdown situations
  • Connect to forward counting: Show that backwards counting undoes forward counting
  • Use visual aids: Number lines going left show decreasing values

Remind your child that backwards counting by 10s follows the same place value rules as forwards counting, just in reverse: usually only the tens digit decreases by 1, and the ones digit stays the same.