Estimating Products

Estimating products by rounding numbers to the nearest ten, hundred, thousand etc., we know how to estimate the sum, difference, etc., to the nearest 10, 100, 1000, etc. Now we have to estimate the products.

In order to estimate products, we round the given factors to the required place value. Estimating products help us to check the reasonableness of an answer.

To estimate the product, we first round off the multiplier and the multiplicand to the nearest tens, hundreds, or thousands and then multiply the rounded numbers.

I. Estimate the products of 34 and 86.

34 ⟶ 30 34 is rounded down to 30

86 ⟶ 90 86 rounded up to 90

34 ⟶ 30

86 ⟶ 90

34 is rounded down to 30

86 rounded up to 90

Calculate mentally 30 × 90 = 2700 

The estimated product is 2700. 


II. Estimate the products of 331 and 267 by rounding to the nearest hundred. 

331 ⟶ 300

267 ⟶ 300

300 × 300 = 90000

The estimated product is 90000.


Consider the following examples on estimating products:

1. Estimate the product: 42 × 57

Solution:

   4 2 →    4 0

× 5 7 → × 6 0

           2 4 0 0 

Thus estimated product = 2400


2. Estimate the product: 47 × 84

Solution:

    4 7 × 8 4         47 is rounded up to 50

      ↓       ↓

    5 0 × 8 0         84 is rounded down to 80

    = 4 0 0 0 

The estimated product = 4000


3. Estimate the product: 74 × 85

Solution:

    7 4 × 8 5         74 is rounded up to 80

      ↓       ↓

    7 0 × 9 0         85 is rounded down to 90

    = 6 3 0 0 

6300 is the estimated product


4. Estimate the product: 358 × 326

Solution:

One number is rounded up and the other is rounded down. Here 358 is rounded up to the nearest hundred, i.e., 400 while 326 is rounded down to the nearest hundred, i.e., 300.

    3 5 8 × 3 2 6         358 is rounded up to 400

        ↓         ↓

    4 0 0 × 3 0 0        326 is rounded down to 300

    = 1 2 0 0 0 0 

120000 is the estimated product



5. Estimate the following product by rounding numbers to the nearest;

(i) Hundred

(ii) Ten ‘341 × 267’

Solution:

(i)     3 4 1 × 2 6 7          341 is rounded up to 300

          ↓         ↓

       3 0 0 × 3 0 0           267 is rounded down to 300

      = 90,000 & The estimated product is 90,000


(ii)     3 4 1 × 2 6 7         341 is rounded down to 340, the nearest ten

          ↓         ↓

      3 4 0 × 2 7 0           267 is rounded up to 270, the nearest ten

       = 91,800 The estimated product is 91,800


Questions and Answers on Estimation in Multiplication:

1. Find the estimated product for each of the given. First one is done for you.

Estimation in Multiplication

Answers:

(b) 70 × 40, 28000

(c) 300 × 100, 30000

(d) 200 × 200, 40000

(e) 700 × 200, 140000

(f) 500 × 400, 200000

(g) 900 × 500, 450000

(h) 3000 × 200, 600000


2. Choose the best estimate and tick the right answer.

I. A shopkeeper has 92 packets of chocolates. If each packet has 37 chocolates, then how many chocolates are there in the shop.

          (i) 3600                             (ii) 4000


II. A museum has 219 marble jars. Each jar has 178 marbles. What is the total number of marbles in the museum?

          (i) 40000                            (ii) 50000


III. There are 76 houses in a locality. Each house uses 278 units of electricity each day. How many units of electricity is used each day in the locality?

          (i) 24000                            (ii) 30000


IV. A hotel has 18 water tanks and each tank has the capacity of 4089 litres of water. What is the total quantity of water that can be stored by the hotel?

          (i) 80000                            (ii) 16000



Answers:

I. (ii)

II. (i)

III. (ii)

IV. (i)

Related Concept

Addition

Word Problems on Addition

Subtraction

Check for Subtraction and Addition

Word Problems Involving Addition and Subtraction

Estimating Sums and Differences

Find the Missing Digits

Multiplication

Multiply a Number by a 2-Digit Number

Multiplication of a Number by a 3-Digit Number

Multiply a Number

Estimating Products

Word Problems on Multiplication

Multiplication and Division

Terms Used in Division

Division of Two-Digit by a One-Digit Numbers

Division of Four-Digit by a One-Digit Numbers

Division by 10 and 100 and 1000

Dividing Numbers

Estimating the Quotient

Division by Two-Digit Numbers

Word Problems on Division






4th Grade Math Activities

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