Estimate to Check Reasonableness

What is the best estimate to check reasonableness of the product for:

421 x 6,124

• 400 x 5,000

• 500 x 6,000

• 400 x 6,000

• 500 x 5,000

When multiplying 1,225 times 204, Gabriel got a product of 24,990. Without solving, does his product seem reasonable? (Hint: use estimation to check for reasonableness)

• Yes, his product is reasonable because I estimated and got a product of 20,000.

• No, his product is not reasonable because I estimated and got a product of 200,000.

• Yes, his product is reasonable because I solved using the standard algorithm and got a product of 24,990.

What is the best estimate to check reasonableness of the product for:

265 x 31

• 200 x 30

• 300 x 40

• 300 x 30

• 200 x 20

Multiply. Estimate to check for reasonableness.

609 x 5 = ______

Multiply. Estimate to check for reasonableness.

8,504 x 3 = _____

Isabelle has 9 ant farms. Each ant farm has 99 ants. Which of the following shows a reasonable estimate of how many ants Isabelle has?

• 7 x 125 = 875

• 8 x 110 = 880

• 9 x 100 = 900

• 10 x 100 = 1,000

Viktor has 7 piles of coins with 63 coins in each. Which is a reasonable number of coins in Viktor’s piles?

• 300, because 7 × 63 is about 7 × 40 = 280

• 360, because 7 × 63 is about 7 × 50 = 350.

• 441, because 7 × 63 is about 7 × 60 = 420.

• 500, because 7 × 63 is about 7 × 70 = 490

Marisa says 302 × 6 = 192. Which of the following shows a reasonable estimate?

• 400x6=2,400

• 300x6=1,800

• 300x10=3,000

• 300x6=900

Estimate 
2 3/8 + 1 7/9

• 3 1/2

• 3

• 4

• 5

Estimate
4/5 + 5/9

• 1

• 1 1/2

• 2

• 0