Page 147 - NUMINO TG_2A

Activity 1

3. The empty boxes represent certain 3 Use subtraction and a related fact to find the missing number.
numbers. Have students use addition and
related facts to find the missing numbers. 12+ =19 +=
Method 1: Use the related addition and =-
subtraction of fact families to find the missing =19-12=7
numbers in the blanks. =17 Use a related fact and subtraction
to find the missing number.
12 7 19 12 7 19
a 9+ =30 b +27=46
7 19 12 12 19 7 =30-9 =46-27
= 21 = 19
Method 2: Use the 4-step method.
Understand the Question c 21+ =42 d +19=45
Q: What are we trying to find? = 21 = 26
A: The missing number.
Plan the Process 4 Read each problem. Write the number sentence to find the
Q: How can we solve it?
A: Use the that represents the missing missing number.
number in the sentence.
Solve the Problem a +12=25
Q: Write an addition sentence 25 is 12 more than an =13
A: 12 25. unknown number.
Look Back
Q: What is the answer? b +16=37
A: 13. The sum of an unknown =21
number and 16 is 37.

80

Express unknown numbers with

Unknown numbers can be expressed using symbols such as , , and . Make an addition or
subtraction sentence using for the unknown number.
Example: If the unknown number and 17 add to 31, what is the unknown number?

Solution: 17 31

31 17 14

Answer: 14

130 NUMINO Teacher s Guide