Unit
1
Facilitator’s Guide G05 ~ Mathematics
Attempt 1: Guess an answer that will make the number sentence TRUE. Guess that a 6 in the block will make the number sentence true. 3 156 – 6 = 3 149
Attempt 2: To choose 6 as the answer will make the number sentence FALSE. Guess another answer. Since 6 is not enough to subtract from 3 156 to get 3 149, you must choose a greater number. Use the number 7. 3 156 – 7 = 3 149
Using this method, it may take a few tries to solve the number sentence. It is time-consuming and not always the best choice.
ACTIVITY 8 1.
Solve the number sentences using trial and improvement. Question
Answer
1.1
1 458 – = 1 443
15
1.4
1 326 – = 1 316
1.2 1.3 1.5
239 + = 343
104
515 + = 1 415
900
14
985 + = 999
10
Checking the solution by substitution is very similar to trial and improvement. You must study the number sentence and then decide on an answer. You then replace the answer in the number sentence and do the calculation. The number sentence must be TRUE. Number sentences are also a way of showing equivalence. What does equivalence mean?
Equivalence is when one side of the number sentence is equal to the other side of the number sentence. In other words, showing that the number sentence is true. Equivalence
The left side of the number sentence is equivalent (equal to) the right side of the number sentence. It means the number sentence is true.
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