Number Sense Challenge
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What you will learn
- 1Review place value and number concepts up to 1 million
- 2Apply rounding, estimation, and comparison skills
- 3Demonstrate number sense through problem solving
Mini Lesson
This challenge reviews Unit 1 skills: place value, comparing numbers, rounding, estimation, and prime and composite numbers. 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.
Words to know
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.
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.
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