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Number Trail Grade 4 / Week 10 / Thursday
4/6
Week 10 · Tenths and hundredths

Thursday

The snail's long day
// Decimals show parts of a whole
⏱ about 15 min

Thursday: The snail's long day

Chris the Coyote settles on a mossy log and adjusts the feather in his hat.

"This is the tale of a very patient snail," he begins.

One morning, Lizzy the Lizard followed a snail with her magnifying glass.

Before lunch, it crawled three tenths of a meter.

After lunch, it crawled four hundredths of a meter more.

Lizzy wanted to add, but tenths and hundredths are different sizes.

Then she remembered that three tenths is thirty hundredths.

Thirty hundredths and four hundredths made thirty-four hundredths of a meter.

"That snail had a long day," Chris chuckles, "for a snail."

Story: Add tenths and hundredths

To add 3/10 + 4/100, make the denominators the same.

Write 3/10 as 30/100.

Then 30/100 + 4/100 = 34/100.

As a decimal, the snail crawled 0.34 meter in all.

A number line from 0.30 to 0.40 in hundredths, with a dot at 0.34
QUESTIONS ABOUT THE STORY
  • Read the question.
  • Tap your answer.
A snailHow far did the snail crawl before lunch?
The snail crawls 3/10 meter, then 4/100 meter. How far in all?
34/100 = ?
ADD TENTHS AND HUNDREDTHS
  • Read the question.
  • Tap your answer.
6/10 + 25/100 = ?
2/10 + 7/100 = ?
45/100 + 3/10 = ?
5/10 + 50/100 = ?
SOLVE THE STORY
  • Read the question.
  • Tap your answer.
Bennie walks 7/10 kilometer, then 15/100 kilometer more. How far does he walk?
Rosie's jar holds 4/10 liter of water. She adds 8/100 liter. How much water now?
Lizzy's sprout grows 1/10 meter, then 9/100 meter. How much does it grow?
WRITE THE SUM AS A DECIMAL
  • Read the question.
  • Tap your answer.
85/100 = ?
48/100 = ?
19/100 = ?
SentenceTrue or false?
3/10 + 4/100 = 34/100?
3/10 + 4/100 = 7/110?
6/10 + 25/100 = 0.85?
2/10 = 20/100?
WHY THIS EXERCISEWe never add the denominators. 3/10 is 30/100, so the sum is 34/100.
Try it
Find a meter stick or a tape measure.
Put your finger on 30 centimeters. That is 0.3 meter.
Slide your finger 4 centimeters more.
Where are you now? Write it as a decimal of a meter.
Draw the snail's path on a number line from 0.30 to 0.40 meter.

What a patient snail! Tomorrow Freddy has a decimal game.

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