Envision 4th Using Reasonableness & Estimating

Ursula has an album in which she keeps pressed flowers. The album has 34 pages, and each page has 7 pressed flowers. Which of the following will give you a reasonable estimate of how many pressed flowers Ursula has?

• 30 x 7 = 210

• 40 x 7 = 280

• 50 x 5 = 250

• 60 x 4 = 240

Tags

4.NBT.A.3

Isabelle has 9 ant farms. Each ant farm has 99 ants. Find the equation that will give you a reasonable estimate for how many ants Isabelle has?

• 7 x 125 = 875

• 8 x 110 = 880

• 9 x 100 = 900

• 10 x 100 = 1,000

The U.S. Soccer organization sent me a flyer that said they had over 500 players. They have 30 teams with 12 players on each sports team. Is this a reasonable number to put on their flyers? There can be more than one.

• No.

  When I round 12 players to 10 and multiply 30 x 10 this equals 300, less than the 500 on flyer.

• Yes.

  When I round 12 to 20 players I get

  30 x 20 = 600, so the 500 on flyer is correct.

• No.

  When I add

  30 + 12 = 42 and 500 is not close to that number.

• No.

  When I multiply

  (30 x 10) and

  (30 x 2) I get

  360 and this is not over 500.

Kenny has 17 pouches of marbles. Each pouch has 23 marbles. Estimate to find about how many marbles Kenny has.

• I round 17 to 20

  and 23 to 30

  20 x 30 = 600 marbles

• I solve for partial products and add

  10 x 20

  10 x 3

  7 x 20

  7 x 3

  = 391

• I round 17 to 10

  and 23 to 20

  10 x 20 = 200 marbles

• I round 17 to 20 and 23 to 20

  20 x 20 = 400 marbles

Viktor has 7 piles of coins with 63 coins in each. Which of these can be a reasonable number of coins in Viktor’s piles? There can be more than one.

• 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. Is this answer reasonable? Which of the following shows a reasonable estimate?

• 2,400 is reasonable because I can round 302 to 400

  400 x 6 = 2,400

• 3000 is reasonable because I can round both numbers

  300 x 10 = 3,000

• 1,800 is reasonable because I can round 302 to 300

  and multiply

  300 x 6 = 1,800

• 900 is reasonable because I can multiply

  300 x 6 = 900

Jaime practiced swimming for about 12 hours every week for 17 weeks. She said she practiced over 204 hours. Which equation would you use to check if her answer was reasonable?

• Her answer is not reasonable because

  I would round

  12 to 10 and

  17 to 10 and multiply

  10x10=100 this is not close to 204

• Her answer is not reasonable

  because

  I would round

  12 to 20 and

  17 to 20 and multiply

  20 x 20 = 400 this is not close to 204

• Her answer is reasonable because I would round 12 to 10

  and 17 to 20 and multiply 10 x 20 =

  200 so this is close to 204

• Her answer is not reasonable because I would round 12 to 10 and multiply

  10 x 17 = 317 this is not close to 204

Alyssa is growing a sunflower she estimated her sunflower will be over 7 feet tall in one month. Is this estimate reasonable?

Remember there are 12 inches in 1 foot.

• Yes, one month is equal to 4 weeks and I can round 64 inches to 60

  4 x 60 = 240 inches which equals 20 ft.

• No, in 4 weeks the sunflower will be 64 inches. If I round 64 to 60 and divide it by

  12 inches

  I get 5 feet

• I can't answer because there is no data for one month

• Yes, because in 4 weeks the plant will be 64 inches so I can round 64 to 60 and multiply by 12 inches

  12 x 60 = 720 inches which equals 60 feet