How to Add Two Fractions Faster

Fractions whose denominators are the same are called similar fractions, otherwise they are called dissimilar fractions. The fractions 1/9 and 7/9 are similar fractions, while 3/4 and 2/3.

Adding similar fractions is easy. Just copy add the numerator and then copy the denominator. For example,

1/9 + 7/9 = 8/9.

Adding dissimilar fractions is a bit more complicated. You have to get the Least Common Multiple (LCM) of the denominators. For example, if we want to add 3/4 and 2/3, we get the LCM of 4 and 3 which is equal to 12. You then change the given to equivalent fractions. The addition becomes

9/12 + 8/12 = 17/12.

Shortcut: How to Add Two Fractions Faster

We can use a shortcut to add to two add fractions.  We will only discuss dissimilar fractions because similar fractions are too easy to add. Below are the steps for the shortcut 3/4 and 2/3 Continue reading

Mental Math: How to Subtract Numbers Faster

In the previous post, we have learned a faster way to add numbers near multiples of 10. In this post, we are going to learn to subtract numbers faster, but first let’s review some basic terms.

In the subtraction

8 – 6 = 2

8 is the minuend, 6 is the subtrahend and 2 is the difference.

In subtracting numbers, numbers may be added to the minuend and subtrahend in order to simplify calculations. The strategy is to change the subtrahend to multiples of ten, hundred, thousands, etc. Doing this will speed up calculation and with enough practice, may be done mentally. Here are some examples.

Example 1

1.) What is 55 – 18?

In this case, 18 is near 20, so we can add 2. If we add 2 to 20, we should also add 2 to 55. So, the expression becomes

(55 + 2) – (18 + 2).

Simplifying, we have 57 – 20 = 37. And really, 55 – 18 = 37.  Continue reading

Mental Math: Adding Numbers Near Multiples of 10

People who are very good at mental math calculations are not all gifted. Some of them just know simple strategies in order to calculate numbers easily and fast.

In this post, I am going to teach you a math trick on adding numbers that will simplify and speed up calculations. With enough practice, you can even use this strategy to perform mental calculations.

This strategy uses numbers that are near multiples of tens, hundreds, thousands, and so on. We can add a certain number to one addend and subtract that number to another addend in order to make one of the addends a multiple of 10. Sounds complicated? Not really.

Example 1:  49 + 36

This looks really hard to calculate mentally, but it’s easier than you think. First, we see that 49 is nearly 50. So, we can add 1 to 49.

This becomes 50 + ? Well, we add 1 to 49, so we have to subtract 1 from 36. So, 36 becomes 35. Therefore, the addition  Continue reading

Percentage Math Trick 3: Making Use of Fractions

In the previous two posts, we have learned two types of calculations about percentage: ignoring the percent sign and making use of 10%. In this post, we learn another math shortcut that is very useful in speed calculations about percentage.

One of the easiest ways to calculate for a percentage of a number is to convert percent into fractions. For example, 50% is equivalent to 1/2 so instead of multiplying the number by 0.5, you can just multiply by one half (or equivalently) divide by 2. Here are some examples.

Example 1

What is 50% of 284?  Continue reading

Percentage Math Tricks: Making Use of 10%

In the previous post, we have learned how to calculate the percentage of a number by ignoring the percent sign. We continue our discussion on the tricks in getting the percentage with a number by making use of 10%.

Calculating 10% of the number is one of the easiest calculations in percentage. To calculate 10% means to get 1/10 of that number. This can be done easily mentally: 10% of 200 is 20 and 10% of 85 is 8.5. As we can see, we just eliminate 0 in the ones place if the number ends with 0 or move the decimal point one digit to the left.  So how do we make use of 10% in making calculations?

Example 1: Multiplies of 10%

What is 20% o 750? Continue reading