We also looked at using a standard algorithm to solve multiplication or division, for larger numbers. This strategy is useful if we need to trade, or regroup.

Apply

QUESTION 1

Let's use the area model to find $29\times28$29×28.

Fill in the areas of each rectangle.

	$20$20	$9$9
$20$20	$\editable{}$	$\editable{}$
$20$20	$\editable{}$	$\editable{}$
$8$8	$\editable{}$	$\editable{}$
$8$8	$\editable{}$	$\editable{}$

Find the sums of each column

	$20$20	$9$9
$20$20	$400$400	$180$180
$20$20	$400$400	$180$180
$8$8	$160$160	$72$72
$8$8	$160$160	$72$72
Total:	$\editable{}$	$\editable{}$
Total:	$\editable{}$	$\editable{}$

What is the total area of the rectangles?

	$20$20	$9$9
$28$28	$560$560	$252$252

So what is $29\times28$29×28?

QUESTION 2

Find the value of $651\div7$651÷7.

QUESTION 3

Find the value of $297\div16$297÷16.

$\editable{}$ with remainder $\editable{}$

Remember!

Arrays and the area model are great to solve multiplication or division problems when there will be no remainder. If we are not sure, we can use a standard algorithm.

Outcomes

5.NBT.B.5

Fluently multiply multi-digit whole numbers (up to three-digit by four-digit factors) using efficient strategies and algorithms.

5.NBT.B.6

Find whole-number quotients and remainders of whole numbers with up to four-digit dividends and two-digit divisors, using strategies based on place value, the properties of operations, and/or the relationship between multiplication and division. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.

PRACTICE: Multiplication and Division

Practice