Elementary School Lessons

Greatest Common factor or GCF is the largest whole number that divides evenly into each of the numbers.

FACTORS are the numbers that you multiply to get another number. [ 3 X 5 = 15 where the factors are 3 and 5]

To get the greatest common factor, one can use two methods:

• First is to list all the factors of the given numbers. The list the common factors or the same factors for these given numbers. When this has been done, choose the biggest number among the common factors.

ex: 30 = 1, 2, 3, 5, 6, 10, 15, 30

20 = 1, 2, 4, 5, 10, 20

The common factors for 30 and 20 are 1,2, 5 and 10 therefore the greatest common factor is 10.

• Another method for finding the greatest common factor is listing down the prime factors. After listing the prime factors, multiply these prime factors.

PRIME FACTORS are numbers that can only be multiplied by 1 and itself [ex: 2,3,5,7,11…]

The prime factors for 30 are 5 x 3 x 2

The prime factors for 20 are 5 x 2 x 2

The prime factorization of 30 and 20 have one 5 and one 2 in common. Multiply these common prime factors and you get the greatest common factor.

5 x 2 = 10

August 11

Math Prep

Ordinal Numbers

1^st first

2^nd second

3^rd third

4^th fourth

5^th fifth

6^th sixth

7^th seventh

8^th eighth

9^th ninth

10^th tenth

Math Word problems

Here are the steps in solving Math word problems:

1. Read and understand the problem carefully.
2. Write the given information.
3. Find out what is asked.
4. Give the number sentence.
5. Solve for the answer.
6. Write the answer with the correct label.

Math Prep

Number Words 10 – 100

10 ten

20 twenty

30 thirty

40 forty

50 fifty

60 sixty

70 seventy

80 eighty

90 ninety

100 one hundred

Addition with Regrouping

• In adding numbers with regrouping, align the digits according to their place values.

• Add the ones first, the tens next, the hundreds, and then the thousands.

• Regroup to the next higher place whenever the partial sum is more than 9.

Addition without Regrouping

• In adding numbers without regrouping, write the numbers in columns, so that the ones digits are at the rightmost column, the tens digits are in the next column, the hundreds digits are the third column and the thousands digits are in the leftmost column.

• Start adding the ones digits, next the tens, then the hundreds and then the thousands digits.

July 29

Math Prep

Number Words 11 – 20

1. eleven
2. twelve
3. thirteen
4. fourteen
5. fifteen
6. sixteen
7. seventeen
8. eighteen
9. nineteen
10. twenty