if a calorie is equivalent to 4.184 joules, how many joules are contained in a 250 kilocalorie slice of pizza?

Question

signtific noation

Answer 1

So we are basically converting the unit from kilocalories to joules.

 

250 kilo-calories = 250 * 1000 calories; [remember that kilo means a multiple of 1000]

 

But one calorie is equivalent to 4.184 joules. Thus, all we need to do now is to multiply the calorie value by 4.184 to get the same amount in joules unit:

 

= 250 * 1000 * 4.184 joules

 

Use a calculator to do the multiplication.

 

Thanks.

 

EDIT: I just saw that you need to express the number in scientific notation. The way to do that is to express the number like this (just an example, not actual answer): 3.1556×10^-5

 

So let's say that we end up getting something like 45612 joules (again, not the actual answer, just use a calculator to perform the above mentioned multiplication). To convert this into a scientific notation, see that the decimal point is basically situated after the last digit '2' (we don't write it since the decimal part is zero in this case, but in general it might not zero, it could have been something like 41209.7782 or something). Anyway, next thing to do would be to move the decimal position towards left so that it falls right after the first digit '4'. To do so, we have reduced the actual number from 45612 to 4.5612, which is 10000 times smaller than it should be. To compensate for this reduction, we multiple this new smaller number by 10⁴, which is just 10 to the power 4. Of course this number is nothing but 10000 (ten thousand) as it should be. Thus, in scientific notation, the number now looks like:

 

45612 = 4.5612×10⁴