Solved Exercises on Counting by 1s, 2s, 5s, and 10s in Grade 1

Master skip counting: counting by 1s, 2s, 5s, and 10s, number patterns, sequences, and number sense through these 5 detailed exercises.

Solution: Exercises 1 to 3
1 Counting by 1s
Exercise 1
Count forward by 1s starting from 67
Write the next 8 numbers:
67, 68, ___, ___, ___, ___, ___, ___, ___
Definition:

Counting by 1s: Adding 1 to each number to get the next number in sequence

Counting by 1s method:
  1. Start with the given number
  2. Add 1 to get the next number
  3. Continue adding 1 for each step
  4. Watch for tens transitions (9→0)
67
Start
68
+1
69
+1
70
+1
71
+1
72
+1
73
+1
74
+1
75
+1
Step 1: Start with 67

67 is our starting number

Step 2: Add 1 to get each next number

67 + 1 = 68, 68 + 1 = 69, 69 + 1 = 70, etc.

Step 3: Continue the pattern

Watch for when units go from 9 to 0 (like 69 to 70)

67, 68, 69, 70, 71, 72, 73, 74, 75
Final answer:

67, 68, 69, 70, 71, 72, 73, 74, 75

Applied rules:

• Counting rule: Each number is 1 more than the previous number

• Tens transition: When units reach 9, tens increase and units reset to 0

• Sequential order: Numbers increase consistently from left to right

2 Counting by 2s
Exercise 2
Count by 2s starting from 24
Write the next 6 numbers:
24, 26, ___, ___, ___, ___, ___, ___
Definition:

Counting by 2s: Adding 2 to each number to get the next number in sequence

24
Start
26
+2
28
+2
30
+2
32
+2
34
+2
36
+2
38
+2
Step 1: Start with 24

24 is our starting number

Step 2: Add 2 to get each next number

24 + 2 = 26, 26 + 2 = 28, 28 + 2 = 30, etc.

Step 3: Notice the pattern

All numbers are even (end in 0, 2, 4, 6, 8)

24, 26, 28, 30, 32, 34, 36, 38
Final answer:

24, 26, 28, 30, 32, 34, 36, 38

Applied rules:

• Skip counting rule: Each number is 2 more than the previous number

• Even pattern: Starting with even, all results are even

• Units digit pattern: Cycles through specific digits

3 Counting by 5s
Exercise 3
Count by 5s starting from 15
Write the next 6 numbers:
15, 20, ___, ___, ___, ___, ___, ___
Definition:

Counting by 5s: Adding 5 to each number to get the next number in sequence

15
Start
20
+5
25
+5
30
+5
35
+5
40
+5
45
+5
50
+5
Step 1: Start with 15

15 is our starting number

Step 2: Add 5 to get each next number

15 + 5 = 20, 20 + 5 = 25, 25 + 5 = 30, etc.

Step 3: Notice the pattern

All numbers end in 0 or 5

15, 20, 25, 30, 35, 40, 45, 50
Final answer:

15, 20, 25, 30, 35, 40, 45, 50

Applied rules:

• Skip counting rule: Each number is 5 more than the previous number

• Fives pattern: Numbers always end in 0 or 5

• Alternating pattern: Ends in 5, then 0, then 5, then 0...

Counting Patterns and Rules
n → n+k
Skip Counting Formula
By 1s
n + 1
Consecutive counting
By 2s
n + 2
Even/odd patterns
By 5s
n + 5
Money and time
By 10s
n + 10
Place value
Key definitions:

Skip counting: Counting by intervals greater than 1

Pattern: A repeated sequence or design

Interval: The fixed amount added each time

Skip counting methodology:
  1. Identify the starting number
  2. Choose the interval (1, 2, 5, or 10)
  3. Add the interval consistently
  4. Recognize the emerging pattern
Tip 1: Count fingers on hands to practice counting by 5s.
Tip 2: Use nickels to practice counting by 5s.
Tip 3: Use dimes to practice counting by 10s.
Tip 4: Practice counting by 2s to learn even numbers.
Common patterns: Counting by 2s: 2,4,6,8,10... Counting by 5s: 5,10,15,20...
Real-world applications: Money counting, time telling, measurement.
Skip counting rules to remember:

• By 1s: n → n+1 (consecutive numbers)

• By 2s: n → n+2 (even or odd numbers)

• By 5s: n → n+5 (ends in 0 or 5)

• By 10s: n → n+10 (same units digit)

Skip Counting Patterns
📊
Counting by 1s
Consecutive numbers, each 1 more than previous
23 → 24 → 25 → 26
Counting by 2s
Even numbers if starting even, odd if starting odd
20 → 22 → 24 → 26
Counting by 5s
Numbers end in 0 or 5
5 → 10 → 15 → 20
Counting by 10s
Only tens digit changes
30 → 40 → 50 → 60
Solution: Exercises 4 to 5
4 Counting by 10s
Exercise 4
Count by 10s starting from 40
Write the next 6 numbers:
40, 50, ___, ___, ___, ___, ___, ___
Definition:

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

40
Start
50
+10
60
+10
70
+10
80
+10
90
+10
100
+10
110
+10
Step 1: Start with 40

40 is our starting number

Step 2: Add 10 to get each next number

40 + 10 = 50, 50 + 10 = 60, 60 + 10 = 70, etc.

Step 3: Notice the pattern

Only the tens digit changes, units stay the same

40, 50, 60, 70, 80, 90, 100, 110
Final answer:

40, 50, 60, 70, 80, 90, 100, 110

Applied rules:

• Skip counting rule: Each number is 10 more than the previous number

• Tens pattern: Only the tens digit increases by 1

• Place value: Adding 10 affects only the tens place

5 Mixed counting patterns
Exercise 5
Identify the pattern and continue:
12, 14, 16, 18, ___, ___, ___
Definition:

Pattern recognition: Identifying the rule that generates a sequence of numbers

12
Start
14
+2
16
+2
18
+2
20
+2
22
+2
24
+2
Step 1: Look at the differences

14 - 12 = 2, 16 - 14 = 2, 18 - 16 = 2

Step 2: Identify the pattern

Each number is 2 more than the previous (counting by 2s)

Step 3: Continue the pattern

18 + 2 = 20, 20 + 2 = 22, 22 + 2 = 24

12, 14, 16, 18, 20, 22, 24
Final answer:

12, 14, 16, 18, 20, 22, 24

Applied rules:

• Difference method: Find the difference between consecutive terms

• Pattern consistency: Same difference indicates arithmetic sequence

• Continuation rule: Apply the same operation to continue

Comprehensive Summary: Counting by 1s, 2s, 5s, and 10s
n → n+k
General Skip Counting Rule
Key definitions:

Counting by 1s: Adding 1 to each number (consecutive counting)

Counting by 2s: Adding 2 to each number (skip counting by twos)

Counting by 5s: Adding 5 to each number (skip counting by fives)

Counting by 10s: Adding 10 to each number (skip counting by tens)

Skip counting: Counting by intervals greater than 1

Arithmetic sequence: Sequence where each term differs by a constant

Complete methodology:
  1. Identify the starting number: Know where the sequence begins
  2. Determine the interval: Find the consistent difference between terms
  3. Apply the rule: Add the interval to each number to get the next
  4. Recognize patterns: Understand the characteristics of each counting method
  5. Verify the sequence: Check that all numbers follow the same rule
Tip 1: Counting by 2s creates even numbers if starting with even, odd numbers if starting with odd.
Tip 2: Counting by 5s always results in numbers ending in 0 or 5.
Tip 3: Counting by 10s only changes the tens digit, keeping the units digit constant.
Tip 4: Use physical objects like fingers, coins, or blocks to visualize counting patterns.
Common patterns: Counting by 2s: 2,4,6,8,10... Counting by 5s: 5,10,15,20... Counting by 10s: 10,20,30,40...
Real-world applications: Money counting (nickels and dimes), time telling (5-minute intervals), measurement.
Essential rules and formulas:

• By 1s: n → n+1 (consecutive numbers)

• By 2s: n → n+2 (arithmetic sequence with common difference 2)

• By 5s: n → n+5 (arithmetic sequence with common difference 5)

• By 10s: n → n+10 (arithmetic sequence with common difference 10)

• General: n → n+k (where k is the counting interval)

Counting Patterns Comparison
📊
Counting by 1s
Every number in sequence, building number sense foundation
1, 2, 3, 4, 5...
Counting by 2s
Efficient counting, introduces even/odd concept
2, 4, 6, 8, 10...
Counting by 5s
Useful for money, time, and grouping
5, 10, 15, 20, 25...
Counting by 10s
Connects to place value, base-10 system
10, 20, 30, 40, 50...
Key takeaways:

• Skip counting builds foundational skills for multiplication

• Each counting method creates distinct patterns

• Understanding patterns improves number sense

• Practice with various starting points strengthens skills

Questions & Answers

Question: Why do we need to learn counting by 2s, 5s, and 10s? Isn't counting by 1s enough?

Answer: Great question! Skip counting is super helpful for many reasons:

  • It's faster: Instead of counting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, you can count 2, 4, 6, 8, 10!
  • It prepares you for multiplication: Counting by 2s is like doing 2×1, 2×2, 2×3, etc.
  • It helps with money: Counting nickels (5¢) and dimes (10¢) uses skip counting
  • It helps with telling time: Minutes on clocks come in 5-minute intervals

Think of skip counting as taking shortcuts - you get to the same place faster!

Example: If you have 6 groups of 2 apples, counting by 2s (2, 4, 6, 8, 10, 12) is quicker than counting each apple individually!

Question: My child can count by 1s fine but gets confused with skip counting. How can I help them understand the concept better?

Answer: Start with concrete examples and gradually move to abstract concepts:

  • Use objects: Count pairs of socks by 2s, groups of 5 pennies, bundles of 10 straws
  • Make it visual: Draw circles around groups of 2s, 5s, or 10s
  • Connect to familiar things: Fingers on hands (5s), pairs of shoes (2s), wheels on cars (4s)
  • Practice regularly: Just 5-10 minutes daily makes a big difference

Start with small ranges (count by 2s to 20) before attempting larger numbers.

Tip: Use songs and rhymes! Many children learn skip counting patterns through music and rhythm.

Question: When I count by 5s, why do the numbers always end in 0 or 5? That's weird!

Answer: That's not weird - it's actually a cool pattern! Here's why:

  • When you start with 5 and add 5, you get 10 (ends in 0)
  • Then 10 + 5 = 15 (ends in 5)
  • Then 15 + 5 = 20 (ends in 0)
  • This pattern keeps repeating: 5, 0, 5, 0...

It's like a pattern that repeats every two numbers! This happens because 5 is half of 10, and our number system is based on 10.

Example: 5, 10, 15, 20, 25, 30 - see how the last digit goes 5, 0, 5, 0, 5, 0?

This pattern helps you check if you're counting by 5s correctly!

Question: How can I help my child practice counting by 10s beyond 100? They seem to struggle once we go past 100.

Answer: Going past 100 can feel like entering new territory! Here are strategies:

  • Emphasize the pattern: Explain that 100+ follows the same pattern as 0-100
  • Use place value: Focus on the hundreds and tens digits changing while units stay constant
  • Connect to real life: Ages, house numbers, prices often go beyond 100
  • Practice in chunks: Count 100-110, then 120-130, etc.

Remind them that 100, 110, 120... works just like 0, 10, 20... but with an extra 1 in front!

Tip: Use a hundreds chart extended to 120 or 150 to show the continuation of patterns!

Question: What's the connection between skip counting and multiplication? Should I teach them together?

Answer: Skip counting is essentially repeated addition, which is the foundation of multiplication!

  • Counting by 2s: 2, 4, 6, 8 is the same as 2×1, 2×2, 2×3, 2×4
  • Counting by 5s: 5, 10, 15, 20 is 5×1, 5×2, 5×3, 5×4
  • Connection: Skip counting provides the multiplication facts naturally

While teaching together isn't necessary, emphasize the connection: "Counting by 3s four times gives us 4 groups of 3, which is 4×3=12."

This connection makes multiplication facts easier to learn and remember!