Using rounding and compatible numbers to extimate products

24×18 rounds to

• 30x20=600

• 20x20=400

• 20x10=200

• 30x10=300

Tags

CCSS.5.NBT.A.4

33×31 is close to

• 40x30=1,200

• 40x40=1,600

• 30x40=1,200

• 30x30=900

Tags

CCSS.4.NBT.B.5

Round to estimate the product

38×22

• 800

• 1,200

• 600

• 900

Round to estimate the product.

45×48

• 2,000

• 2,500

• 1,600

• 2,160

Tags

CCSS.4.NBT.A.3

CCSS.4.OA.A.3

39×19 rounds to

• 30x20=600

• 30x10=300

• 40x20=800

• 40x10=400

Tags

CCSS.4.NBT.A.3

72×48 rounds to

• 80x50=4,000

• 80x40=3,200

• 70x40=2,800

• 70x50=3,500

Lenore rounds each factor to the nearest ten

to estimate that the product of 52×38

is 1,500. Is her estimate reasonable?

• yes

• no

Estimate the product using compatible numbers.

24×18

• 25x20=500

• 30x20=600

• 20x10=200

• 24x18=432

Estimate the product using compatible numbers.

24×37

• 24x37=888

• 30x40=1,200

• 25x40=1,000

• 20x30=600

Tags

CCSS.4.NBT.A.3

CCSS.4.NBT.B.5

CCSS.4.OA.A.3

Estimate the product using compatible numbers.

52×27

• 50x25=1,250

• 50x20=1,000

• 52x27=1,404

• 60x30=1,800

Tags

CCSS.4.NBT.B.5