How do you write 21 divided by 3?
21 divided by 3 equals 7, which you can write as the equation 21 ÷ 3 = 7.
Split twenty-one into three equal groups, and each group lands on seven. You can also express this as 21/3, which simplifies to 7. Honestly, this is one of those division facts that sticks with you because it's so clean.
What are all the factors of 21?
The positive factors of 21 are 1, 3, 7, and 21.
Factors are simply numbers that divide 21 without leaving a remainder. Don't overlook the negative side: -1, -3, -7, and -21 work too. The prime factors? Just 3 and 7, since 21 = 3 × 7. Add up all the positive factors (1 + 3 + 7 + 21) and you get 32—fun little math trick, isn't it?
What are not factors of 21?
Numbers like 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 are not factors of 21.
These numbers just don't play nice with 21. Try dividing 21 by 2 and you get 10.5—not a whole number. Only numbers that give you whole results when dividing 21 count as factors. It's that straightforward.
What can divide into 20?
The factors of 20 are 1, 2, 4, 5, 10, and 20.
These numbers divide 20 cleanly. Think in pairs: 1 and 20, 2 and 10, 4 and 5. The prime factorization? That's 2 × 2 × 5, or 2² × 5. Handy to know when you're breaking down numbers.
What is the common multiple of 21?
The first 10 multiples of 21 are 21, 42, 63, 84, 105, 126, 147, 168, 189, and 210.
A common multiple is just a number that both 21 and another number share. Since 21 × 1 = 21, 21 × 2 = 42, and so on, these are all multiples of 21. Each one's also a multiple of 7, because 21 is 3 × 7.
What is the HCF of 21?
The highest common factor (HCF) of 21 is 21 itself.
Compare 21 to another number, like 35, and the HCF drops to 7. But for 21 alone, the largest number dividing it evenly is itself. Need the HCF of 21 and another number? List the common factors and pick the biggest one.
How do you show 20 divided by 5?
20 divided by 5 equals 4, which you can show as 20 ÷ 5 = 4 or as the fraction 20/5.
Split twenty into five equal groups and each group has four. This is one of those basic division facts you'll use all the time—like splitting a $20 pizza bill four ways.
What can 42 be divided by?
42 can be divided evenly by 1, 2, 3, 6, 7, 14, 21, and 42.
These are all the factors of 42. Check it: 42 ÷ 1 = 42, 42 ÷ 2 = 21, and so on. The prime factorization? That's 2 × 3 × 7.
How do you solve 7 divided by 3?
7 divided by 3 equals 2 with a remainder of 1, or 2⅓ as a mixed number.
Divide seven by three and you get two whole groups of three, with one left over. As a decimal, that's about 2.333. You can also write it as 7/3.
What are the factors of 15 and 21?
The factors of 15 are 1, 3, 5, and 15; the factors of 21 are 1, 3, 7, and 21.
To find the greatest common factor (GCF), look for the biggest number in both lists. Here, it's 3. You can use the divide and conquer technique or just list the factors—either way works.
What are the common factors of 7 and 21?
The common factors of 7 and 21 are 1 and 7.
Since 7 is prime, its only factors are 1 and itself. And because 21 is 3 × 7, its factors include 1 and 7. The greatest common factor? That's 7.
What is the HCF of 21 and 29?
The highest common factor (HCF) of 21 and 29 is 1.
29 is prime, so its only factors are 1 and 29. The factors of 21 are 1, 3, 7, and 21. The only overlap? Just 1, making the HCF 1.
What are factors of 18?
The factors of 18 are 1, 2, 3, 6, 9, and 18.
These numbers divide 18 without a trace. Think in pairs: 1 and 18, 2 and 9, 3 and 6. The prime factorization? That's 2 × 3 × 3, or 2 × 3².
What’s the prime factorization of 20?
The prime factorization of 20 is 2 × 2 × 5, or 2² × 5.
Prime factorization breaks a number down to its prime building blocks. For 20, start with 20 = 4 × 5, then break 4 into 2 × 2. That gives you 2 × 2 × 5.
What are the multiples of 5?
The multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50.
Multiples are what you get when you multiply 5 by whole numbers (5 × 1 = 5, 5 × 2 = 10, etc.). Keep adding 5 and you'll get more. These patterns pop up everywhere—counting money, scheduling, you name it.
