Understanding Decimal Numbers
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Questions and Answers

Consider the numbers 0.4599 and 0.46. Which statement accurately describes their relationship after rounding each to the nearest hundredth?

  • Both numbers round to 0.45, indicating they are approximately equal when considering only tenths.
  • 0.4599 rounds to 0.46 and 0.46 remains unchanged, but 0.4599 was smaller to begin with. (correct)
  • Both numbers round to 0.46, suggesting they are nearly equivalent when considering hundredths.
  • 0.4599 rounds to 0.45 while 0.46 remains unchanged, demonstrating a clear difference at the hundredths place.

A scientist measures two chemicals for an experiment. Chemical A weighs 0.145 grams, and Chemical B weighs 0.08 grams. Which correctly calculates the total weight of both chemicals and expresses the difference in significant figures?

  • 0.2250 grams, adding a zero to match the number of decimal places in Chemical A's weight.
  • 0.22 grams, truncating to the nearest hundredth to match the shorter decimal's precision.
  • 0.23 grams, rounding to the nearest hundredth to reflect the least precise measurement. (correct)
  • 0.225 grams, retaining all decimal places from the calculation.

You need to divide 17.25 by 2.5. What is the correct procedure and result?

  • Both A and B are correct.
  • Convert 17.25 to 1725, convert 2.5 to 25, divide to get 69.
  • Convert 2.5 to 25, adjust 17.25 to 172.5, divide to get 6.9. (correct)
  • Divide directly; the result is 6.9.

A recipe requires 2.25 cups of flour. You only want to make half the recipe. How many cups of flour do you need, and based on your measuring tools (measuring cups with increments of 0.25 cups), how should you practically measure it?

<p>1.125 cups, use 1 cup plus half of a quarter cup. (C)</p> Signup and view all the answers

When converting the fraction $\frac{5}{16}$ to a decimal, the result is a repeating or terminating decimal. Identify the correct decimal representation and explain why it terminates or repeats.

<p>0.3125, terminates because the denominator's prime factors are only 2 and 5. (D)</p> Signup and view all the answers

You have the repeating decimal 0.363636... where '36' repeats indefinitely. What is this decimal expressed as a simplified fraction?

<p>$\frac{36}{99}$ which simplifies to $\frac{4}{11}$ (C)</p> Signup and view all the answers

A store offers a discount of 15% on an item originally priced at $24.99. If sales tax is 6%, what is the final price after the discount and sales tax?

<p>$22.40, achieved by multiplying the original rate by 1.06 after taking 15% off. (B)</p> Signup and view all the answers

Consider the following expression: 3. 14 + (15.8 / 2.5) - 2.75 * 1. 2. Following the correct order of operations, what is the final result, rounded to the nearest hundredth?

<p>9.89, achieved by correctly following the order of operations. (B)</p> Signup and view all the answers

Flashcards

What are Decimals?

Numbers that include a whole number part and a fractional part, separated by a decimal point.

Decimal Place Value

The value of a digit based on its position after the decimal point (tenths, hundredths, etc.).

Fraction to Decimal

Divide the numerator (top number) by the denominator (bottom number).

Decimal to Fraction

Write the decimal as a fraction with a denominator of 10, 100, 1000, etc., then simplify.

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Comparing Decimals

Compare whole numbers first, then tenths, hundredths, and so on, adding zeros to align.

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Rounding Decimals

If the digit to the right is 5+, round up; if less than 5, round down.

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Adding/Subtracting Decimals

Vertically align decimal points, then add/subtract as with whole numbers, keeping the decimal point in the same place.

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Multiplying Decimals

Multiply as whole numbers, then count the total decimal places in the factors to place the decimal in the product.

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Study Notes

  • Decimals represent numbers that are not whole numbers
  • They are written using a base-10 system, separated by a decimal point

Decimal Place Values

  • The position of a digit after the decimal point determines its value
  • Tenths: The first digit after the decimal point (0.1)
  • Hundredths: The second digit after the decimal point (0.01)
  • Thousandths: The third digit after the decimal point (0.001)
  • Ten-thousandths: The fourth digit after the decimal point (0.0001)
  • And so on, each place being a power of 10 smaller than the previous one

Converting Fractions to Decimals

  • Divide the numerator by the denominator

Converting Decimals to Fractions

  • Write the decimal as a fraction with a denominator of 10, 100, 1000, etc.
  • Simplify the fraction if possible

Comparing Decimals

  • Start by comparing the whole number parts.
  • If the whole number parts are the same, compare the tenths place, then the hundredths place, and so on.
  • Add zeros to the end of shorter decimals to make comparison easier.

Rounding Decimals

  • Identify the place value you are rounding to.
  • Look at the digit to the right of that place value.
  • If the digit is 5 or greater, round up. If it is less than 5, round down.

Adding and Subtracting Decimals

  • Align the decimal points vertically.
  • Add or subtract as you would with whole numbers.
  • Carry or borrow as needed.
  • Place the decimal point in the answer directly below the decimal points in the problem.

Multiplying Decimals

  • Multiply the numbers as if they were whole numbers.
  • Count the total number of decimal places in the factors.
  • Place the decimal point in the product so that it has the same number of decimal places as the total counted in the factors.

Dividing Decimals

  • If the divisor is a decimal, move the decimal point to the right until it becomes a whole number
  • Move the decimal point in the dividend the same number of places.
  • Divide as you would with whole numbers.
  • Place the decimal point in the quotient directly above the decimal point in the dividend.

Word Problems Involving Decimals

  • Read the problem carefully.
  • Identify the key information and what you are being asked to find.
  • Determine the operation needed (addition, subtraction, multiplication, division).
  • Solve the problem and check your answer for reasonableness.

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Description

Explore decimal numbers, their place values (tenths, hundredths, thousandths), and how to convert between fractions and decimals. Learn to compare decimals by examining whole number parts and decimal places, adding zeros for alignment.

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