Estimating the Results of Operations-II

We know how to estimate Sum and Difference of numbers by rounding off the numbers

Now, we shall learn how to estimate the results of multiplication of numbers.

Estimating the Results of Product of numbers

First we find the product of the two numbers.

The product of two numbers is as shown,

Now let us find the estimate of the product by rounding off the numbers

331 is rounded off to 300 and 267 is rounded off to 300

And now multiply the estimated numbers as shown,

The estimate(90000) is reasonable as it is closer to the actual product( 331x267=88377 ) of the numbers.

Example 2

First find the product of the two numbers.

The product of the two numbers is as shown,

Now let us find the estimate of the product by rounding off the numbers

Both the numbers get rounded off to 3000 rounding off to the nearest thousands

And now multiply the estimated numbers as shown,

The estimate(9000000) is not reasonable as it is not closer to the actual product(9411600) of the numbers.

So the numbers in a calculation should be rounded off to a place depending on the number of digits in them

In this case as the numbers have 4 digits, we would round off the numbers to hundreds place to get a reasonable estimate.

Consider the same two numbers and Round off to hundreds place as shown,

And now multiply the estimated numbers as shown,

The estimate is reasonable as it is closer to the actual product (9411600) of the numbers.

Revision

Rounding off of numbers is done basing on the number of digits present in them

The End