Front-End Estimation

This procedure work well when doing addition and subtraction, because we round and add the numbers located the leftmost column, and the remaining numbers are converted to zero.

For example: suppose we want to add two numbers that are both in the

thousands:

3767 + 1345

Solution

Round the first number to the nearest hundred: 3767 when rounded is equal to 4000.

1345, when rounded to the nearest number is equal to 1000

Add those two digits together as thousand: 4000 + 1000 = 5000

And the approximated number is 5000

Example

Estimate by using front-end estimation

936 + 885

Solution

Before the front-end calculation, Let us some rounding off.

900 + 900

Now, let us add the two leftmost numbers.

9 + 9 = 18

Add two zeros after the 18

You now have 1800, which is the approximated answer.

As in addition, the same principle can be applied foe subtraction.

Example

Estimate by using front-end estimation

3457 - 1450

Solution

First, locate which number that is located to the leftmost column, which is 3

First, locate which number that is located to the leftmost column, which is 1

Now, let's subtract:        3 - 1 = 2

Let's add or annex three zero after the 2.

You now have 2000, that is the  approximated answer.

Remaining numbers that are located after the leftmost are converted to zero.