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Number Trail Grade 5 / Week 03 / Friday
5/6
Week 03 · Multiply big numbers

Friday

Freddy's multiplying game
// Partial products and the standard algorithm
⏱ about 15 min

Friday: Freddy's multiplying game

Freddy the Frog sits on a lily pad with a stack of cards.

"Ribbit! Today each card has a multiplying puzzle," he says.

"Some cards look back at tens, tenths and decimals too."

Lucy the Ladybug takes a calm breath. "I am ready," she says.

Bennie the Bear sits on a log nearby.

"Remember the rows, and check with an estimate," he says.

Freddy flips the first card with a happy croak.

Game 1: Partial products

FIND THE PRODUCT
  • Read the question.
  • Tap your answer.
23 × 15 = ?
64 × 37 = 1,800 + 420 + ? + 28
80 × 50 = ?

Game 2: The standard algorithm

MULTIPLY
  • Read the question.
  • Tap your answer.
87 × 46 = ?
315 × 28 = ?
2,104 × 36 = ?
659 × 14 = ?

Game 3: Estimate

ROUND, THEN MULTIPLY
  • Read the question.
  • Tap your answer.
Round 588 to the nearest hundred. Then multiply by 21.
Round 49 and 62 to the nearest ten. Then multiply.
FIND THE SLIP
  • Read the question.
  • Tap your answer.
Riley says 46 × 27 = 414. What did he forget?
Rosie says 315 × 28 = 3,150. Use an estimate. Is that reasonable?
Hazel says 87 × 46 = 4,002. Is she right?

Game 4: Look back

TENS, TENTHS AND DECIMALS
  • Read the question.
  • Tap your answer.
3.5 × 100 = ?
0.6 ? 0.58
46 × ? = 4,600
LEAST TO GREATEST PRODUCT
  • Find or estimate each product.
  • Put them from least to greatest.
11st
22nd
33rd
44th

Game 5: True or false?

SentenceTrue or false?
87 × 46 = 4,002?
315 × 28 = 8,820?
659 × 14 = 9,326?
80 × 50 = 400?
WHY THIS EXERCISE659 × 14 is 9,226, and 80 × 50 is 4,000.
Try it
Pick two numbers from a calendar, like 24 and 31.
Multiply them on paper with two rows.
Estimate to check your answer.

Ribbit! You multiplied like a champ. Tomorrow is a Number Hunt.

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