PORCENTAGEM - Professora Angela Matemática

Summary

In this video, the speaker discusses the concept of percentages, tracing their origins back to ancient Rome. The explanation covers how percentages, initially expressed as fractions, evolved over time into the modern decimal system. Examples are provided, demonstrating how to calculate percentages such as 8% of 400 and 32% of 1,200. The speaker explains different methods to convert percentages into decimals and fractions, making complex calculations more accessible. Viewers are encouraged to engage with the content, share it, and learn that solving percentage problems is not as difficult as it may seem.

Takeaways

• 😀 Percentages have a long history, dating back to the Roman Empire, where Emperor Augustus introduced a 1% tax on transactions.
• 😀 The modern use of percentages began in the 15th century, with Italian scribes shortening the term 'per cento' to 'percent'.
• 😀 Percentages can be represented as fractions, with 9% being equivalent to 9/100 or 9 hundredths.
• 😀 A percentage can be converted into a decimal by moving the decimal point two places to the left (e.g., 9% = 0.09).
• 😀 25% as a percentage equals 25/100, which can be converted into a decimal as 0.25.
• 😀 The speaker demonstrates the process of calculating 8% of 400, where 8% is converted to 0.08 and multiplied to give 32.
• 😀 250% is equal to 250/100, which simplifies to 2.5 when converted into a decimal, leading to the result of 1000 when multiplied by 400.
• 😀 To calculate percentages more easily, you can convert them to decimals (e.g., 32% = 0.32) and multiply by the given number (e.g., 0.32 × 1200 = 384).
• 😀 Another method to calculate percentages involves dividing the total amount by 100 (e.g., 1200 ÷ 100 = 12) and then multiplying by the percentage value (e.g., 12 × 32 = 384).
• 😀 The speaker encourages viewers not to find percentage calculations difficult and to share the video for further clarity and understanding.
• 😀 Throughout the video, practical examples are used to illustrate different percentage calculations, making it easier to grasp the concept.

Q & A

What is the historical origin of percentages?

The use of percentages dates back to the Roman Empire, where Emperor Augustus imposed a 1% tax on transactions at auctions.

When did the modern concept of percentages emerge?

The modern concept of percentages appeared in the 15th century, when Italian scribes began to abbreviate the expression 'per cento' to represent percentages.

How is 9% expressed as a fraction?

9% is equivalent to 9/100 or nine hundredths.

How can 9% be written as a decimal?

9% can be written as 0.09 when converted to a decimal.

What is the decimal form of 25%?

25% is equivalent to 0.25 in decimal form.

How is 250% converted to a decimal?

250% is equivalent to 2.50 in decimal form, which can be simplified to 2.5.

How do you calculate 8% of 400?

To calculate 8% of 400, you can multiply 0.08 by 400, resulting in 32.

What is the alternative method to calculate 8% of 400?

Alternatively, you can treat 8% as 8/100, simplify the fraction, and multiply it with 400, which also results in 32.

How do you calculate 32% of 1200?

To calculate 32% of 1200, multiply 0.32 by 1200, which equals 384.

Can the fraction method be used to calculate 32% of 1200?

Yes, you can calculate 32% as 32/100, simplify the fraction, and multiply it by 1200, which also gives the result of 384.