Solved Exercises on Reading and Writing Numbers to 100 in Grade 1

Master reading and writing numbers to 100: place value, number words, expanded form through these 3 detailed exercises.

Solution: Exercises 1 to 3
1 Place Value
Exercise 1
What is the place value of each digit in the number 47?
Write the number in expanded form.
Definition:

Place value: The value of a digit depends on its position in the number. In 2-digit numbers, the positions are TENS and ONES.

Place value method:
  1. Identify the position of each digit (tens, ones)
  2. Determine how many tens and how many ones
  3. Write the expanded form: tens + ones
TENS PLACE
4
ONES PLACE
7
Step 1: Identify each digit's position

In 47: 4 is in the tens place, 7 is in the ones place

Step 2: Determine the value of each digit

4 in tens place = 4 tens = 40, 7 in ones place = 7 ones = 7

Step 3: Write the expanded form

47 = 40 + 7

47 = 40 + 7
Final answer:

Digit 4 represents 4 tens (40), digit 7 represents 7 ones (7). Expanded form: 47 = 40 + 7

Applied rules:

• Place value: Each position has a specific value (tens, ones)

• Expanded form: Express a number as the sum of the values of its digits

• Counting: 4 tens means 4 groups of 10 = 40

2 Number Words
Exercise 2
Write the number 83 in words.
Then write the number word "sixty-five" in numerals.
Definition:

Number words: The written form of numbers using letters instead of digits.

83 = Eighty-three
Sixty-five = 65
Step 1: Convert 83 to words

8 in tens place = eighty, 3 in ones place = three, combine with hyphen: eighty-three

Step 2: Convert sixty-five to numerals

Sixty = 60 (6 tens), five = 5 (5 ones), combine: 65

Step 3: Check the conversion

Eighty-three = 83 ✓, Sixty-five = 65 ✓

Final answer:

83 in words is "eighty-three", "sixty-five" in numerals is 65

Applied rules:

• Hyphenation: Use hyphens for compound numbers 21-99 (except multiples of ten)

• Word order: Tens word first, then ones word (forty-two, not two-forty)

• Special cases: Numbers 11-19 have unique names (eleven, twelve, thirteen, etc.)

3 Expanded Form
Exercise 3
Write the expanded form of 94.
Then convert 50 + 8 back to standard form.
Definition:

Expanded form: A way to write numbers showing the value of each digit.

94 = 90 + 4
50 + 8 = 58
Step 1: Identify place values in 94

9 is in tens place (9 × 10 = 90), 4 is in ones place (4 × 1 = 4)

Step 2: Write expanded form

94 = 90 + 4 (the sum of each digit's value)

Step 3: Convert 50 + 8 to standard form

50 (5 tens) + 8 (8 ones) = 58

Final answer:

Expanded form of 94 is 90 + 4, Standard form of 50 + 8 is 58

Applied rules:

• Expanded form: Each digit multiplied by its place value

• Standard form: The normal way we write numbers (digits)

• Addition: Combine tens and ones to get the total

Rules and methods, laws,...
57 = 50 + 7
Expanded Form
Place Value
Tens + Ones
Position determines value
Number Words
Twenty-one = 21
Written form of numbers
Expanded Form
45 = 40 + 5
Value of each digit
Key Rule: In 2-digit numbers, the left digit represents tens and the right digit represents ones.
Hyphen Rule: Use hyphens for compound numbers 21-99 (twenty-one, thirty-five).
Tip 1: Remember that 10 ones make 1 ten (10 = 1 ten, 20 = 2 tens).
Tip 2: Practice counting by tens (10, 20, 30, ..., 100) to understand place value.
Tip 3: Use visual aids like base-10 blocks to understand tens and ones.
Number Patterns to Know:

• Numbers 11-19: eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen

• Tens: ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety, one hundred

• Compound numbers: twenty-one through ninety-nine (use hyphens)

100 = 10 tens
Hundred Concept
10
20
30
40
50
60
70
80
90
100
Additional Exercises
4 Number Recognition
Exercise 4
Identify the number represented by 7 tens and 3 ones.
Write the number in standard form and in words.
Definition:

Number composition: Combining tens and ones to form a 2-digit number.

7 tens + 3 ones = 70 + 3 = 73
Step 1: Calculate the value of tens

7 tens = 7 × 10 = 70

Step 2: Calculate the value of ones

3 ones = 3 × 1 = 3

Step 3: Add tens and ones together

70 + 3 = 73

73 = Seventy-three
Final answer:

The number is 73 (standard form), seventy-three (word form)

Applied rules:

• Composition: Combine tens and ones to form the complete number

• Place value: Tens digit goes first, ones digit goes second

• Word formation: Use the tens word followed by the ones word

5 Number Sequence
Exercise 5
Count from 45 to 55, writing each number in words.
Then identify the pattern in the ones place.
Definition:

Number sequence: A set of numbers following a specific order or pattern.

45
46
47
48
49
50
51
52
53
54
55
Step 1: Write each number in words

45=fifty-five, 46=fifty-six, 47=fifty-seven, 48=fifty-eight, 49=fifty-nine, 50=fifty

51=fifty-one, 52=fifty-two, 53=fifty-three, 54=fifty-four, 55=fifty-five

Step 2: Observe the pattern

From 45 to 49: ones digits increase 5→6→7→8→9

At 50: tens digit increases (4→5), ones digit resets to 0

From 51 to 55: ones digits increase 1→2→3→4→5

Step 3: Identify the pattern

Ones place cycles through 0-9, then tens place increases by 1

Final answer:

Pattern: Ones place increases by 1 until 9, then tens place increases and ones resets to 0

Applied rules:

• Number sequence: Each number is one more than the previous

• Place value pattern: Ones place cycles 0-9, then tens place increments

• Counting: Understanding the relationship between adjacent numbers

Key Concepts for Reading and Writing Numbers to 100
64 = 6 tens + 4 ones
Place Value
Key definitions:

Place value: The value of a digit based on its position in a number

Standard form: Writing numbers with digits (47)

Word form: Writing numbers with words (forty-seven)

Expanded form: Breaking apart a number by place value (47 = 40 + 7)

Complete methodology:
  1. Identify place value: Recognize tens and ones positions
  2. Determine digit value: Calculate how many tens and ones
  3. Convert between forms: Move between standard, word, and expanded forms
  4. Verify accuracy: Check that conversions are correct
Tip 1: Remember that 10 ones equal 1 ten (10 = 1 ten).
Tip 2: When writing numbers in words, use hyphens for compound numbers (twenty-one, thirty-five).
Tip 3: The tens digit tells you how many groups of 10, the ones digit tells you extra units.
Tip 4: Practice with visual aids like base-10 blocks to reinforce the concept of tens and ones.
Common errors: Mixing up tens and ones, forgetting hyphens in compound numbers, misreading numbers ending in zero.
Exam preparation: Practice converting between all three number forms, memorize number words for 11-19, learn tens from 20-100.
Key Rules to Remember:

• Place value: In 2-digit numbers, left digit = tens, right digit = ones

• Hyphens: Use for compound numbers 21-99 (except multiples of ten)

• Number words 11-19: Have unique names (eleven, twelve, thirteen, etc.)

• Tens words: Twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety

• Expanded form: Sum of each digit's place value (57 = 50 + 7)

Questions & Answers

Question: I don't understand why 47 is "forty-seven" and not "fourty-seven". Why does it change from "four" to "forty"?

Answer: Great observation! This is a special rule in English number words. When forming the tens (10, 20, 30, 40, etc.), the word changes from the ones digit:

  • 4 (four) becomes 40 (forty)
  • 5 (five) becomes 50 (fifty)
  • 8 (eight) becomes 80 (eighty)
  • 9 (nine) becomes 90 (ninety)

These special forms for tens developed historically in the English language. The "y" ending indicates it's a multiple of 10. So 47 becomes "forty-seven" because it's 4 tens (forty) and 7 ones (seven).

Note: Some numbers like "thirteen" and "fifteen" also have special forms that don't match the ones digit exactly.

Question: When I write 85 in expanded form, is it 8 + 5 or 80 + 5? How do I know which is correct?

Answer: The correct expanded form of 85 is 80 + 5, not 8 + 5. Here's why:

In the number 85:

  • The 8 is in the TENS place, so it represents 8 tens = 8 × 10 = 80
  • The 5 is in the ONES place, so it represents 5 ones = 5 × 1 = 5

Expanded form shows the VALUE of each digit based on its position:

85 = 80 + 5 (expanded form)

If you added 8 + 5, you'd get 13, which is much smaller than 85. That's how you know it's incorrect.

Always remember: expanded form shows what each digit is worth based on its place in the number.

Question: My child is struggling with the concept of place value. Are there any hands-on activities to help them understand tens and ones?

Answer: Absolutely! Hands-on activities are excellent for understanding place value:

  • Base-10 blocks: Use rods for tens (10 cubes connected) and individual cubes for ones
  • Grouping objects: Bundle 10 straws or sticks together with a rubber band to represent tens
  • Cups and beans: Put 10 beans in small cups (tens) and loose beans (ones)
  • Abacus: Move beads in columns representing tens and ones

Activities to try:

  • Have your child build numbers with blocks and then write the expanded form
  • Play "Guess the Number" where you describe tens and ones (e.g., "I have 3 tens and 7 ones")
  • Use a hundreds chart to see patterns in tens and ones

Visual and tactile learning helps children internalize that the position of a digit determines its value.