Question

Estimate the following products using the general rule: $5281\times 3491$.

Answer 1

Hint: We will first round off the given numbers using the general rule of rounding off.

The General rule states that 

• We round numbers in tens to the nearest ten.

• We round numbers in the hundreds to the nearest hundred.

• We round numbers in the thousands to the nearest thousand. and so on..

Using this rule, we will round off the given two numbers. After Rounding off we will multiply those numbers to find the estimated product of the given numbers.

Complete step by step answer:

To estimate a number, we first round off the number using general rule, which is, we look at the digit to the right  of the digit that we want to round off,  if it is less than 5, then  value of digit is not changed, if the digit to the right is 5 or more than 5, then the value of digit which we are rounding off get replaced by its successor and all the other digits to the right of digit that we rounded off are replace by zeroes.

Now, to find the estimated product of the given question, we start with rounding of our numbers, that is 5281 and 3491.

We will round off 5281 to the nearest thousand, so we get 5000.

We will round off 3491 to the nearest thousand, so we get 3000.

To find estimated product, we multiply this rounded off numbers, as follows:

$5000\times 3000$ 

$=5\times 1000\times 3 \times 1000$ 

$=5\times 3\times 1000 \times 1000$ 

$=15 \times 1000000$ 

$=15,000,000$ 

Hence, the estimated product of 5218 and 3491 is 15000000.

Note: This method only gives us an estimate of the product of two numbers, that is, to which value the product will be near. This is not the exact value. This is only estimated value by rounding off and hence should not be used where exact values are required.