Ray's New Primary Arithmetic by Joseph Ray Ray's New Primary Arithmetic by Joseph Ray    

Lesson 40: Subtract Numbers From Up to 12

Directions

Teach children to subtract numbers from up to 12.

Have children practice until they perfectly master the task.

Steps

STEP 1

• Children separate a larger group of up to 12 objects into two smaller groups.
• Repeatedly separate a group of objects into smaller groups per the table below. For example, 3 pencils from 4 pencils leaves 1 pencil, 8 coins from 11 coins leaves 3 coins, and 9 cars from 12 cars leaves 3 cars, etc.

• When children are ready, have them separate the object groups themselves.
• Children must perfectly master the operations listed in the table before proceeding to the next phase of the lesson.

STEP 2

• Children separate groups of objects they can't see, but can imagine (bears, mountains, trees).
• Using the table above as a guide, ask children to call out the answer to questions such as, 'How many are one shoe from four shoes?' and 'How many are nine frogs from twelve frogs?'
• Give numerous exercises on each number, with constant reviews, until children can recite each operation in the table with great accuracy and rapidity.

STEP 3

• In this phase, do not mention objects. Children subtract numbers directly.
• Using the table above as a guide, ask children to call out the answer to questions such as, 'How many are one from four?' and 'How many are four from seven?'
• Give numerous exercises on each number, with constant reviews, until children can perform each operation with great accuracy and rapidity.

STEP 4

• Direct children to practice writing and reciting the subtraction problems listed in the table above. For example, they would write and then recite:
• 3 from 12 leaves 9
• 12 minus 3 is 9
• 12 - 3 = 9
• Repeat for each combination in the table until the children master the tasks.

STEP 5

Have children copy, solve, and recite the following table:

• 11 + 1 or 1 + 11 = ; therefore 12 - 1 = ; 12 - 11 =
• 10 + 2 or 2 + 10 = ; therefore 12 - 2 = ; 12 - 10 =
• 9 + 3 or 3 + 9 = ; therefore 12 - 3 = ; 12 - 9 =
• 8 + 4 or 4 + 8 = ; therefore 12 - 4 = ; 12 - 8 =
• 7 + 5 or 5 + 7 = ; therefore 12 - 5 = ; 12 - 7 =
• 6 + 6 = ; therefore 12 - 6 = ;

STEP 6

• Assess mastery by reading aloud the word problems below and having the children mentally compute and recite the solutions. If children have difficulties, repeat the prior phases and then reassess.