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Question

Sunila had \(9\frac{1}{4}\) kg of flour to make bread with. If the recipe says that she needs  \(1\frac{1}{8}\) kg to make one loaf of bread, how many loafs can she make? Estimate to the nearest whole number.

The correct answer is

8

Solving the Bread Baking Word Problem

This problem asks us to find out how many loaves of bread Sunila can make given the total amount of flour she has and the amount required per loaf. We are also asked to estimate the final answer to the nearest whole number. The amounts are given as mixed fractions.

Understanding the Problem Quantities

Sunila has a total amount of flour:

  • Total flour = \(9\frac{1}{4}\) kg

The amount of flour needed for one loaf of bread is:

  • Flour per loaf = \(1\frac{1}{8}\) kg

To find out how many loaves she can make, we need to divide the total amount of flour by the amount of flour needed for one loaf.

Number of loaves = \(\text{Total flour} \div \text{Flour per loaf}\)

Converting Mixed Fractions to Improper Fractions

Before dividing, it's easier to work with improper fractions. We convert each mixed fraction:

  • Total flour: \(9\frac{1}{4} = \frac{(9 \times 4) + 1}{4} = \frac{36 + 1}{4} = \frac{37}{4}\) kg
  • Flour per loaf: \(1\frac{1}{8} = \frac{(1 \times 8) + 1}{8} = \frac{8 + 1}{8} = \frac{9}{8}\) kg

Dividing the Fractions

Now we divide the total flour (\(\frac{37}{4}\)) by the flour per loaf (\(\frac{9}{8}\)):

Number of loaves = \(\frac{37}{4} \div \frac{9}{8}\)

Dividing by a fraction is the same as multiplying by its reciprocal. The reciprocal of \(\frac{9}{8}\) is \(\frac{8}{9}\).

Number of loaves = \(\frac{37}{4} \times \frac{8}{9}\)

We can simplify this multiplication by cancelling common factors before multiplying. Notice that 4 is a factor of 8.

Number of loaves = \(\frac{37}{\cancel{4}^1} \times \frac{\cancel{8}^2}{9}\)

Now, multiply the numerators and the denominators:

Number of loaves = \(\frac{37 \times 2}{1 \times 9} = \frac{74}{9}\)

Estimating to the Nearest Whole Number

The exact number of loaves is \(\frac{74}{9}\). To estimate this to the nearest whole number, we can perform the division:

\(\frac{74}{9} \approx 8.222...\)

To estimate to the nearest whole number, we look at the first digit after the decimal point. If it is 5 or greater, we round up. If it is less than 5, we round down.

In 8.222..., the first digit after the decimal point is 2, which is less than 5.

Therefore, we round down to the nearest whole number.

Estimated number of loaves = 8

Sunila can make approximately 8 loaves of bread.

Step Calculation Result
Convert Total Flour to Improper Fraction \(9\frac{1}{4} = \frac{(9 \times 4) + 1}{4}\) \(\frac{37}{4}\) kg
Convert Flour Per Loaf to Improper Fraction \(1\frac{1}{8} = \frac{(1 \times 8) + 1}{8}\) \(\frac{9}{8}\) kg
Divide Total Flour by Flour Per Loaf \(\frac{37}{4} \div \frac{9}{8} = \frac{37}{4} \times \frac{8}{9}\) \(\frac{74}{9}\)
Convert Result to Decimal (approx) \(\frac{74}{9}\) \(8.222...\)
Estimate to Nearest Whole Number Round \(8.222...\) 8 loaves

Conclusion on Estimated Loaves

Based on the calculation and estimation, Sunila can make approximately 8 loaves of bread with the amount of flour she has.

Revision Table: Checking Calculations

Operation Detail Verification
Mixed to Improper Conversion \(9\frac{1}{4}\) \(9 \times 4 = 36\), \(36+1=37\), fraction is \(\frac{37}{4}\). Correct.
Mixed to Improper Conversion \(1\frac{1}{8}\) \(1 \times 8 = 8\), \(8+1=9\), fraction is \(\frac{9}{8}\). Correct.
Fraction Division \(\frac{37}{4} \div \frac{9}{8}\) Equals \(\frac{37}{4} \times \frac{8}{9}\). Correct.
Fraction Multiplication/Simplification \(\frac{37}{4} \times \frac{8}{9}\) \(4\) goes into \(8\) two times. \(\frac{37}{1} \times \frac{2}{9} = \frac{74}{9}\). Correct.
Estimation to Nearest Whole Number \(8.222...\) Decimal part 0.2 is less than 0.5, so round down to 8. Correct.

Additional Information: Fraction Operations and Estimation

Understanding how to work with fractions is key to solving many math problems, especially those involving recipes or measurements.

  • Mixed Numbers: A mixed number combines a whole number and a fraction, like \(9\frac{1}{4}\). They are useful for representing quantities greater than one.
  • Improper Fractions: An improper fraction has a numerator greater than or equal to its denominator, like \(\frac{37}{4}\). Improper fractions are often easier to use in calculations like multiplication and division.
  • Dividing Fractions: To divide one fraction by another, you multiply the first fraction by the reciprocal of the second fraction. The reciprocal of a fraction is found by flipping the numerator and denominator. For example, the reciprocal of \(\frac{a}{b}\) is \(\frac{b}{a}\).
  • Estimation: Estimating helps you find a value that is close to the exact answer. Rounding to the nearest whole number involves looking at the tenths digit. If it's 5 or more, round up the whole number. If it's less than 5, keep the whole number as it is.

These concepts are fundamental for solving problems involving fractions and real-world quantities like ingredients in a recipe.

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Important Questions from Fractions

  1. If three-fifths of a number is 54, what is two-ninth of it?

  2. The value of \(\frac{{11}}{5} - \left( {\frac{2}{3}of\frac{3}{5} - \frac{1}{5}} \right) + \left( {\frac{6}{5} \div \frac{4}{5}} \right)\) is:

  3. In his career, a tennis player won 5 matches lost 12 matches and had 3 matches as draw. The fraction of the match he lost in his career is:

  4. Simplify:

    \(62\div 5 - \left(\frac{8}{9}\times \frac{18}{7}\right)\times \frac{7}{5}+\frac{5}{4}\times \frac{16}{25}\)

  5. The value of 8 + \((\frac{1}{2} + \frac{1}{4})\) × 16 is:

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