4th Grade - Estimate If An Answer Is Reasonable

 
     
 
     
 
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4th
Reasoning
Estimate if an Answer is Reasonable
Use estimation to verify the reasonableness of calculated results.
Estimate to check the results of addition, subtraction, division, and multiplication problems.
 

Sample Problems

(1)

Estimate the sum:

6,878

+4,217


(11,000)

(2)

Find the compatible number to estimate the quotient:

375 ÷ 6 = _____ (360 ÷ 6 = 60)

(3)

Find the difference. Estimate.

4,190

- 2,816


(1,374)

Estimate: _______ (1,000)

(4)

Estimate the product:

$25.67

x 4


(26 x 4 =104)

(5)

Use the chart to calculate the actual distance and estimated distance that the Jamming Jets Track team ran during practice for one week.


Day of the week

Actual distance

(miles)

Estimated Distance

Monday

5.2

(5)

Tuesday

7.4

(7)

Wednesday

3.1

(3)

Thursday

9.7

(10)

Friday

4.6

(5)

Total miles ran

(30)

(30)

What did you notice about your total for the estimated and calculated amounts? (They are the same, estimating would really be beneficial in this problem)

Learning Tips

(1)

Estimate money

Play a game with your child with estimating money. You can provide your child with play money (Monopoly money or http://www.moneyinstructor.com/play.asp - website has printable fake money). Pretend you are having a yard sale and place prices on different items in your home (especially toys). Your child will have to estimate if he/she has enough money to buy the items wanted.

(2)

Rules for Rounding

Steps to rounding:

  1. Identify the place of the digit that you need to round

  2. Look at the digit to its right, if it is 0, 1, 2, 3, or 4, the digit you are rounding stays the same; if the digit to the right is 5,6,7,8, or 9, the digit you are rounding increases by one.

The digits after the one you have rounded become zeros

(3)

Give a reasonable estimation:

Fill containers with various items (candy, fruit, beans, water, pretzels, etc.) Ask your child what would be a reasonable estimated amount in the container. You can relate the measurements to (weight, total # of items, length, etc.). In the beginning you can give them choices like, what is more reasonable 50 or 100 beans in the jar? Later, you can have them estimate on their own.

Practice measurement units (i.e. ft. yd. mi, in. cups, oz, gal. etc.)

(4)

How much will we spend?

Use the sales papers from different stores and have your child shop for items. Have them estimate the costs and determine about how much will be spent at the store. Once your child has determined his/her estimated budget. Have them calculate the exact total and see if the amounts were close.

(5)

Rounding Decimals

Round to the nearest whole number and eliminate the decimal.


For example, 43.7 = 44


Estimating Quotients

When estimating quotients (division) you cannot just round to the nearest place value because the divisor may not be able to divide evenly. You will have to find the compatible number (numbers that are easy to compute mentally).


For example, 193 ÷ 3 cannot be changed to 200 ÷ 3 because 200 cannot be divided by 3 evenly.

A more compatible number would be 180 ÷ 3 = 60 or 210 ÷ 3 = 70.

Use simple division, ad the remaining zeros.


Extra Help Problems

(1)

Find the sum. Estimate.

7,739

+4,596

(12,335)


Estimate: _____ (12,000)

(2)

Find the sum. Estimate.

6,372

+1,846

(8,218)


Estimate: _____ (8,000)

(3)

Estimate the sum.

8,942

+ 1,463

(10,000)

(4)

Write the missing digit for the estimated sum.


24,397

+□1,144

70,000

(5)

(5)

Write the missing digit for the estimated sum.

9,318

+ 32,425

90,000

(5)

(6)

Find the difference. Estimate.

6,372

- 2,468

(3,904)


Estimate: _______ (4,000)

(7)

Find the difference. Estimate.

3,061

- 1,827

(1,234)


Estimate: _______ (1,000)

(8)

Insert the digit for the estimated difference.

9,190

- □,816

6,000


(2)

(9)

Estimate the product:

903

x 7


(6,300)

(10)

Estimate the product:

8,126

x 22


(160,000)

(11)

Estimate the product:

$57.23

x 8


(60 x 8 =480)

(12)

Find the compatible number to estimate the quotient:

349 ÷ 5 = _____ (350 ÷ 5 = 70)

(13)

Find the compatible number to estimate the quotient:

720 ÷ 7 = _____ (700 ÷ 7 =100)

(14)

Find the compatible number to estimate the quotient:

158 ÷ 8 = _____ (160 ÷ 8 = 20)

(15)

Find the compatible number to estimate the quotient:

175 ÷ 2 = _____ (180 ÷ 2 = 90)

(16)

Find the compatible number to estimate the quotient:

2,861 ÷ 4 = _____ (2,800 ÷ 4 = 700)

(17)

Find the compatible number to estimate the quotient:

2,447 ÷ 6 = _____ (2,400 ÷ 6 = 400)

(18)

Problem Solve:

Andrea works as a zoo guide. She has 4 tours each day. Her first tour is 2.3 miles, second tour is 3.3 miles, third tour is 1.9 miles and fourth tour is 0.8 miles? What is the reasonable estimate of the distance of Andrea’s tours each day?

  1. 8 miles

  2. 18 miles

( 8 miles)

(19)

Problem Solve:

Jeremy has 2 dollars, 2 quarters and 5 dimes. He wants to buy lunch for $4.79, how many more dollars does he need?

(about 3 dollars)

(20)

Problem Solve:

Why is it helpful to estimate to see if an answer is reasonable?

-Answers may vary

(If your exact number is close to your estimate it is a good probability that your answer is correct, it saves time on re-calculating)

(21)

What is the reasonable estimate:


The distance from Los Angeles, CA to Pasadena, CA

  1. 2,000 miles

  2. 20 miles


(20 miles)


(22)

What is the reasonable estimate:


The amount of water in a fish tank

  1. 100 gallons

  2. 1 oz


(100 gallons)

(23)

What is the reasonable estimate:

The amount of milk in a baby’s bottle

  1. 1 cup

  2. 40 gallons


( 1 cup)

(24)

What is the reasonable estimate:

The weight of a refrigerator:

  1. 200 lbs

  2. 1 lb


(200 lbs)

(25)

What is the reasonable estimate:

The length of a car:

  1. 8 ft.

  2. 80 ft.


(8 ft.)

 

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