Note: This problem reviews finding intervals of minutes from Topic A and leads directly into rounding intervals of minutes to the nearest ten in this lesson. Encourage students to share and discuss simplifying strategies they may have used to solve.
Count by ones from 12:17 to 12:20, then by fives to 12:45.
Count by tens and ones, 12:27, 12:37, plus 8 minutes.
Subtract 17 minutes from 45 minutes.
Let’s round 28 minutes to the nearest 10 minutes.
How many tens are in 28? 2 tens
What is 1 more ten than 2 tens? 3 tens
What number is halfway between 20 and 30? 25
In unit form, what number is halfway between 2 tens and 3 tens? 2 tens 5 ones
Estimate to draw a tick mark halfway between 20 and30. Label it 25 = 2 tens 5 ones.
When you look at your vertical number line, is 28 more than halfway or less than halfway between 20 and 30? 28 is more than halfway between 2 tens and 3 tens.
What is 28 rounded to the nearest ten? 30.
In unit form, 2 tens 8 ones rounded to the nearest ten is 3 tens.
Let’s go back to our Application Problem. How would you round to answer the question,
“About how long was the ballet recital?”
The ballet recital took about 30 minutes. Rounded to the nearest ten, the ballet recital took 30 minutes.
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