Lesson 4

Patterns in Addition and Subtraction

Est. Class Sessions: 2–3

Developing the Lesson

Part 2: Adding Dimes

Direct students' attention to the 100 Chart page in the Student Activity Book Reference section. Display five dimes and ask students to find the value of the collection of coins. Ask a student to explain how he or she knew the value of the coins.

Then ask:

X
  • If you were telling your little brother how to find the value of the dimes, how would you explain it to him? (skip count by tens: 10¢, 20¢, 30¢, 40¢, 50¢)
  • Why is counting dimes easy? (It is skip counting
    by tens.)
  • How do you show skip counting by tens on the 100 Chart? (Move to the row below for each ten counted.)

Use the display of the 100 Chart to demonstrate how to skip count on the chart to add tens to a number
(e.g., 23 + 10, 23 + 20, 46 + 10).

Then place a nickel next to the dimes.

Ask:

X
  • How much money is there now? (55¢)
  • What is the number sentence? (50¢ + 5¢ = 55¢)
  • How do you know? Show how you solved it. (Five dimes are worth 50¢ by skip counting on the 100 Chart; to add 5¢ count 5 spaces across on the 100 Chart.)

Next, take away the coins and display three nickels and three pennies. Ask a student to tell the total. Have students locate the total, 18¢, on their 100 Chart.

Add one dime and ask:

X
  • How much money have I added? (1 dime, 10¢)
  • How can you add this dime to 18¢ using the 100 Chart? (Move to one row below, 28¢.)
  • What's the number sentence? (18¢ + 10¢ = 28¢)
  • What if I add 3 dimes? How much does that add? (30¢)
  • How can you add 30¢ using the 100 Chart? (Move on the 100 Chart three rows below 18.)

Guide students to place their fingers on 18, then move below one row for each dime, counting along with you, 18, 28, 38, 48.

Ask:

X
  • What is the number sentence? (18¢ + 30¢ = 48¢)
  • What do you notice about the answer when you add dimes? Is there a pattern? (Possible responses: The ones digit in the answer is the same as the ones digit in the addend. You can skip count by tens to get the tens.)

Give the students a few more similar problems to solve, where the first number is not a multiple of ten and the second one is, such as 23¢ + 40¢, 14¢ + 20¢, etc. Have them count by tens using the 100 Chart. Discuss the patterns they see.

Assign the Skip Counting by Dimes pages in the Student Activity Book. Students use the 100 Chart to solve the problems. Remind them to include the cents label in the number sentences so that it is clear what the numbers represent [MPE6].

Adventure Book:
Student Activity Book: 469 470
Answers
X
SG_Mini
+
X
SG_Mini
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Master: