2nd Grade
Math Remediation Lessons
Unit 10 – Subtraction of Two Digit Numbers: Part 1
Lesson Objectives
Lesson 1: Subtract Tens and Ones
· Subtract 2-digit numbers without regrouping
Remediation:
-Have students to work in pairs of two. Provide matches, rocks, or any other small object. Place a number of them on a table and show how it is easier to count them in groups of ten. First you make groups of ten, then count the ten-groups separately and the individuals separately. Say (for example), "I have here five ten-groups, and four ones." Then you can count another amount of objects by grouping them first into groups of tens, and counting the ten-groups and the ones separately. Use the groups to solve 2-digit subtraction problems without regrouping. (www.homeschoolmath.net)
Website:
http://www.mathmastery.com/math/subtraction/Column-Subtraction-with-Regrouping/Regrouping-Tens-and-Ones-with-Subtraction-/1 Online Tutorial of Subtracting tens and ones with regrouping
Lesson 2: Mental Math Subtraction
· Count back by ones to subtract.
· Count back by tens to subtract.
Remediation:
· Have 3 different colors of index cards. The first stack will have subtraction problems that are single digit problems. The second stack will have problems that are double digit. The third stack will have problems that are three digit numbers. On the index card write a subtraction problem that can worked mentally. Write the answer on the opposite side of the card. Students will pick a card from the first stack and find the answer without the use of pencil or paper. Once they have an answer they will turn over the card and check. If they have the correct answer they can move on to the next stack. If they miss an answer, they have to go to the previous stack and work their way back up.
Website:
http://www.netagency.co.uk/keyedin2/mental.html Mental Math Addition and Subtraction Games
Lesson 3: Regrouping for Subtraction
· Subtract tens and ones with regrouping.
Remediation:
-Tell the students about "houses" and have them draw two houses in a row or put up 2 house drawings on the board. We have the ones house and the tens house. Throughout the lesson, refer to the "houses." Remind them that they should always begin any math problems with the "ones" house. You can (for example) name the houses OTTO ONES and TAMMY TENS. Explain to students (for example) that if Otto does not have enough hotdogs to feed his friends he needs to go to the house next door (Tammy's) and borrow a pack of ten.
- A way to help them visualize what they are doing is to think of the bottom number as the people, and the top number as the apples in a tree. This way they will be reminded to start at the bottom and look up to see the apples for correct subtraction. If there are not enough apples in the tree, they must go next door to the tens house and take one of the tens and add it to the apples to have enough for the people on the bottom. (www.proteacher.org)
Lesson 4: Model and Record Subtraction
· Subtract two-digit numbers with regrouping.
Remediation:
- Use connecting cubes (multi-link cubes) as a manipulative to illustrate regrouping. For example, build 90 (9 groups of ten) and then take away 42. The students will have to "break a ten" to get the 2 ones that they need to remove. Teach them to remember BBBB--bigger bottom (number), better borrow (from the tens). Do this activity for several problems that may be on a worksheet or on the board. (www.proteacher.org)
Lesson 5: Subtract with Regrouping
· Subtract tens and ones with regrouping.
Remediation:
- Teach your students this poem about regrouping. Have them circle the larger number in the ones place, if they seem to have trouble knowing whether to regroup or not. Then have them refer to the poem.
SUBTRACTION RHYME
More on top?
No need to stop!
More on the floor?
Go next door.
Get one ten.
That's ten ones more.
Numbers the same?
Zero's the game!
Lesson 6: Subtract Money
· Subtract money amounts less than a dollar by regrouping.
Remediation:
- Have available play (or real) dimes and pennies, and a die. The idea of this game is to be the first player left with no money. To begin, give each child (in pairs or groups of 3) 50 cents in dimes. One child throws the die. If they throw a 3 ,for example, they can get rid of three pennies, but to do this they have to exchange a dime at the bank. They then give 3 pennies to the banker. The child to get rid of all their money first is the winner. Near the end of the game it gets very exciting, as they have to throw the correct number to get rid of their last few pennies. This game gives them the idea of exchanging. If some students are ready, you can advance the game to dollars. Give them one dollar to start. This means they have no dimes or no pennies, so they will have to do a double swap to subtract what they throw on the die.
- Buy or make some receipt pads like those used in diners for a dinner ticket. Then make a menu using 2 digit numbers. For example, have one side of the menu list sandwiches and the other side list beverage choices. Give students a total amount of money to spend. They can write their own menu ticket and then add to find their total and subtract to find their change.
Lesson 7: Add to Check
· Add to check subtraction.
Remediation:
- Create a table (3X3). Place numbers in some of the squares and some leave blank, as shown below. Students can add or subtract across and down to see the inverse relationship of addition and subtraction. Great self-checking review (the sums of the answers across = the sums of the answers down making it possible for the children to check their own answers)
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http://www.kidzone.ws/math/farm/t_math.asp?gr2-magicsub.html
http://www.kidzone.ws/math/jungle/t_math.asp?gr2-magicsub.html
http://www.kidzone.ws/math/ocean/t_math.asp?gr2-magicsub.html
Lesson 8: More Regrouping Decisions
· Subtract 2-digit whole numbers, with and without regrouping.
Remediation:
- Use twizzlers as a ten model and mini marshmallows for the ones and demonstrated regrouping using the treats.
- Play a game with your students called "sticks and stones". They each have a game mat, which is a sheet of paper divided into three columns. Title the columns ones, tens, and hundreds. They play in groups of twos. Each group has a spinner, a good supply of unifix cubes or snap together cubes, and their mat. One child spins the spinner and puts that many cubes in his ones column. On his next spin, if he has enough (10 cubes) to make a stick he will snap them together and put them in the tens column with the others left over (the stones) in the ones column. Then the other child does the same thing, spinning twice and forming a number. The students will then subtract their two numbers from each other using the cubes.
Subtraction Websites:
http://math.pppst.com/subtraction.html Subtraction Games
http://superteacherworksheets.com/subtraction.html Subtraction Worksheets
http://www.kidzone.ws/math/dynamic2.htm