Question

If 1 calorie is the same as 4.184 J, how many calories are in 42.0 kJ?

Answer 1

the answer is 10038.24 calories

Step-by-step explanation

remember

`\begin{gathered} 1\text{ Kj=1 kilojulie=1000 julies} \\ hence \\ 42\text{ Kj=42}\cdot1000\text{ julies=42000 julies} \\ \end{gathered}`

we can solve this by using a rule of three.

Step 1

let x represents the number of calories in 42 Kj

so

if

`\begin{gathered} 1\text{ calorie}\rightarrow4.184\text{ julies} \\ \end{gathered}`

then

`x\text{ calories}\rightarrow42000\text{ julies}`

as the proportion is the same

`(1)/(4.184)=(x)/(42000)\text{ equation}`

Step 2

solve the equation

`\begin{gathered} (1)/(4.184)=(x)/(42000)\text{ equation} \\ croos\text{ multiply} \\ 1\cdot42000=4.184x \\ \text{divide both sides by 4.184} \\ (42000)/(4.184)=(4.184x)/(4.184) \\ x=10038.24\text{ calories} \end{gathered}`

so, the answer is 10038.24 calories.

I hope this helps you