Mathnasium #MathsTricks: Percentages

Welcome to Mathnasium’s Maths Tricks series. Today we are finding the percentage amount of any number.

To calculate the percentage of a number, we use the following steps:

1. Estimate the answer by rounding the number to the nearest multiple of 50 and using mental maths.
2. Convert the percent to a decimal.
3. Multiply the number by the decimal.
4. Check for reasonableness using your estimate.

Follow the example below to find the percentage.

Example: It takes Larissa 363 total minutes to get from her house to her grandmother’s house. If 87% of this time is spent on a train, how many minutes does she spend on the train?

Step 1: Estimate the answer by rounding the number to the nearest multiple of 50.
Rounding the number 363 to the nearest multiple of 50, we get 350.
Since 87% means 87 for each 100, we estimate 87% of 350, which is equal to 304.5 minutes.

Step 2: Convert the percent to a decimal.
87% is eighty seven hundredths. To write this as a decimal, the digits in 87 all  move 2 places to the right, leaving us with 0.87.

Step 3: Multiply the number by the decimal.
Multiplying the number 363 by the decimal 0.87, we get an answer of 315.81 minutes.

Step 4: Check for reasonableness.
Our estimate was 304.5, so 315.81 is very reasonable.

Answer: 315.81 minutes.

Now, with this strategy, you are ready to use this Mathnasium Maths Trick to find any percentage of any number by converting the percentage to a decimal and multiplying it by the number. Click here for more practice problems, then check your answers here.

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