GMAT Prep - Math - Arithmetic - Adding and Subtracting Decimals by Knewton

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When adding or subtracting decimals, the most important thing to remember is that you must always align the decimal points of the two numbers that you are adding or subtracting. If you don't do this, you'll be very prone to making an error and misalign the place values of the two different numbers. Let's take a look at this example:

82.1 + 4.067 =

82.1 has one digit to the right of the decimal point and 4.067 has three digits to the right of the decimal point. When we line up the decimal points, we see that 4.067 has two digits (the 6 and 7) extending out to the right beyond 82.1. We fill in these gaps with two trailing zeros following the one so that the number reads 82.100. Once we do this, we can do addition in the natural way.

Let's look at a subtraction example:

100 - 9.45 =

100 has no decimal point, but 9.45 has two digits to the right of the decimal point. Therefore, we're going to align the decimal points again and write the nine under the last zero in 100. This will leave gaps to the right of the decimal point in 100. We fill those in with two trailing zeros.

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[EhEhEhification]

@mysconnie No calculators for the GMAT

[afton53]

presented very well and made it very easy to understand.

[mysconnie]

But don't most people just use calculators?

[arunasree2020]

Good about adding and subtracting decimal nice and good expression.

[MusaKusa]

good stuff.

[lld1903]

Clear to understand and useful information.

[cowboybill104]

Informative, but a little fast moving. The decimal in the result does not align exactly with the decimal points above, but it could if a different font were used.

[thatcrazyqbanita]

Very informative and helpful GMAT Math preparation video. Math is my weakness, yet I found this video to break down math processes in a way were they are made simpler and more accessible.

[quertyou]

Your videos are very helpful in reviewing math thanks.

[ConcordTurk]

Good examples of a classic math concept.