# Why is the efficiency in the below question 0.25 not 0.33?

Jun 5, 2018

See below.

#### Explanation:

The total amount of energy released by the heat engine per cycle is sum of the used amount and the wasted amount:

$300 J + 900 J = 1200 J$

Now, given that only $300 J$ of the total $1200 J$ is actually used to do work (and the rest wasted) then the efficiency will be:

$\frac{300}{1200} = \frac{1}{4} = 0.25$