Questions: food energy content when eaten ------------ cal kcal kJ a cup of grapefruit juice 1.15 × 10^5 4.81 × 10^2 a baked potato 2.20 × 10^5 220. 9.20 × 10^2 three ounces of cooked sirloin steak 2.39 × 10^5 1.00 × 10^3

food energy content when eaten
------------
cal kcal kJ
a cup of grapefruit juice 1.15 × 10^5 4.81 × 10^2
a baked potato 2.20 × 10^5 220. 9.20 × 10^2
three ounces of cooked sirloin steak 2.39 × 10^5 1.00 × 10^3

Transcript text: \begin{tabular}{|l|c|c|c|} \hline \multirow{2}{*}{ food } & \multicolumn{3}{|c|}{ energy content when eaten } \\ \cline { 2 - 4 } & cal & kcal & kJ \\ \hline a cup of grapefruit juice & $1.15 \times 10^{5}$ & $\square$ & $4.81 \times 10^{2}$ \\ \hline a baked potato & $2.20 \times 10^{5}$ & 220. & $9.20 \times 10^{2}$ \\ \hline \begin{tabular}{l} three ounces of cooked sirloin \\ steak \end{tabular} & $2.39 \times 10^{5}$ & $\square$ & $1.00 \times 10^{3}$ \\ \hline \end{tabular}

Solution

Solution Steps

Step 1: Understanding the Conversion Factors

To convert between different units of energy, we need to understand the conversion factors:

$1 \, \text{cal} = 0.001 \, \text{kcal}$
$1 \, \text{cal} = 4.184 \, \text{J}$
$1 \, \text{kcal} = 4.184 \times 10^{3} \, \text{J} = 4.184 \, \text{kJ}$

Step 2: Converting Calories to Kilocalories

For the grapefruit juice:

Given: $1.15 \times 10^{5} \, \text{cal}$
Conversion: $(1.15 \times 10^{5} \, \text{cal}) \times 0.001 = 115 \, \text{kcal}$

For the sirloin steak:

Given: $2.39 \times 10^{5} \, \text{cal}$
Conversion: $(2.39 \times 10^{5} \, \text{cal}) \times 0.001 = 239 \, \text{kcal}$

Final Answer

Energy content of a cup of grapefruit juice in kcal: $\boxed{115 \, \text{kcal}}$
Energy content of three ounces of cooked sirloin steak in kcal: $\boxed{239 \, \text{kcal}}$

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