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 86 rounded |

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.**

**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

● Check for Subtraction and Addition

● Word Problems Involving Addition and Subtraction

● Estimating Sums and Differences

● Multiply a Number by a 2-Digit Number

● Multiplication of a Number by a 3-Digit Number

● Word Problems on Multiplication

● 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

● Division by Two-Digit Numbers

**4th Grade Math Activities**

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