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Number Trail Grade 3 / Week 04 / Monday
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Week 04 · Missing numbers

Monday

Find the missing factor
// Unknowns, turn-arounds and break-aparts
⏱ about 15 min

Monday: Find the missing factor

Samantha the Squirrel bounces along a branch with her acorn stash.

"I have 48 acorns, and I packed them in 8 bags," she chatters.

"Every bag holds the same number. But I forgot how many!"

Bennie the Bear writes on a flat stone: 8 × ? = 48.

"The question mark is the unknown," he says.

"We can find it with a fact we know."

Learn it: what times 8 makes 48?

The unknown stands for a number we have not found yet.

8 × ? = 48 asks: 8 groups of what make 48?

Skip count by 8: 8, 16, 24, 32, 40, 48.

That is 6 eights, so the unknown is 6.

Check it: 8 × 6 = 48.

A rectangle of unit squares, eight rows of six
FIND THE MISSING FACTOR
  • Read the question.
  • Tap your answer.
A rectangle of unit squares, eight rows of six8 × ? = 48
5 × ? = 35
? × 9 = 36
? × 6 = 18
USE THE PICTURE
  • Read the question.
  • Tap your answer.
Three equal groups with seven dots in each group3 × ? = 21
Dots in four rows of five? × 5 = 20
A rectangle of unit squares, six rows of nine6 × ? = 54
Two equal groups with eight dots in each group16 = 2 × ?
SAMANTHA'S STASH
  • Read the question.
  • Tap your answer.
An acorn7 × ? = 28
Samantha hides 6 acorns in each of 6 holes. How many acorns?
A tree? × 5 = 45
70 = 10 × ?
SentenceTrue or false?
8 × 6 = 48?
5 × 7 = 40?
4 × 9 = 36?
6 × 9 = 48?
WHY THIS EXERCISE5 × 7 = 35, and 6 × 9 = 54.
SOLVE 8 × ? = 48
  • Think about how Bennie solves it.
  • Tap the steps in order.
1First
2Next
3Then
4Last
Try it
Count out 24 small things.
Make 4 equal piles.
How many are in each pile?
Write it as 4 × ? = 24, then fill in the unknown.
On paper, draw an array that shows 3 × ? = 15.

Great detective work! Tomorrow we find unknowns in division.