🔢 MathGrade 4Lesson 33
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Number Sense Challenge

Lesson preview: the Mini Lesson and Vocabulary are open to everyone. Guided practice, exercises, the parent checklist and the printable PDF worksheet come with full access (free 7-day trial or membership).

Learning Objectives

  • 1Review place value and number concepts up to 1 million
  • 2Apply rounding, estimation, and comparison skills
  • 3Demonstrate number sense through problem solving
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Mini Lesson

This challenge reviews Unit 1 and Unit 2 skills: place value, comparing numbers, rounding, factors, and multiples. Use everything you have learned to show your number sense.

Place Value and Large Numbers

  • Read large numbers using the place-value chart: Millions | Hundred Thousands | Ten Thousands | Thousands | Hundreds | Tens | Ones.
  • Identify the value of any digit by its position: the digit 7 in 4,735,021 is in the hundred-thousands place, so its value is 700,000.
  • Compare numbers by looking at the greatest place value first.

Rounding and Estimation

  • Round up when the digit to the right is 5 or greater.
  • Round down when the digit to the right is less than 5.
  • Estimation helps check if answers are reasonable: round each number first, then operate.

Prime and Composite Numbers

  • Prime numbers have exactly 2 factors: 1 and themselves (e.g. 2, 3, 5, 7, 11, 13).
  • Composite numbers have more than 2 factors (e.g. 4, 6, 8, 9, 12, 15).
  • The number 1 is neither prime nor composite.
Place Value Review ChartPlace Value ReviewMillionsH-ThouT-ThouThousandsHundredsTensOnes34567893,456,789three million, four hundred fifty-six thousand,seven hundred eighty-nineDigit 7 is in Hundreds: value = 700Each place is 10 times the place to its right.
Number Concepts SummaryNumber Concepts SummaryPrime NumbersCompositeExactly 2 factors:1 and itself2, 3, 5, 7, 11, 13More than 2 factorse.g. 12: 1,2,3,4,6,124, 6, 8, 9, 12, 15Rounding RulesRound UPif next digit is 5 or moree.g. 3,847 to nearest 100 = 3,900Round DOWNif next digit is less than 5e.g. 3,847 to nearest 1000 = 4,000
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Tip: to find all factors of a number, check every whole number from 1 up to the number itself and list every pair that multiplies to give that number.

Vocabulary
place value
The value of a digit based on its position in a number.e.g. In 4,735,021 the digit 7 is in the hundred-thousands place.
rounding
Replacing a number with a nearby simpler value.e.g. 3,847 rounded to the nearest thousand is 4,000.
estimation
A rough calculation to check whether an answer is reasonable.e.g. Estimate 198 + 403 as 200 + 400 = 600.
prime number
A whole number greater than 1 with exactly two factors: 1 and itself.e.g. 7 is prime because only 1 and 7 divide it.
composite number
A whole number with more than two factors.e.g. 12 is composite because 1, 2, 3, 4, 6, and 12 all divide it.
factor
A number that divides another number exactly with no remainder.e.g. 4 is a factor of 12 because 12 ÷ 4 = 3.
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← Lesson 32: Explore Symmetry and PatternsLesson 34: Operations Challenge →