If a gas furnace releases 420 kcal of heat energy, what is the energy in kilojoules? (1 cal = 4.184 j)

The furnace releases 1757280 J 

Explanation:
We will do the conversion on two steps:
1- convert the kcal to cal
2- convert the cal to J

Step 1: converting kcal to cal
1 kcal is equivalent to 1000 cal. Therefore:
420 kcal is equivalent to 420*1000 = 420000 cal

Step 2: converting cal to J
We are given that:
1 cal = 4.184 J
Therefore:
420000 cal is equivalent to 420000 * 4.184 = 1757280 J 

Hope this helps :)

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