John raises butterflies. He has 4 jars of 10 caterpillars each. 40% of them fail to become butterflies, but the rest become caterpillars.  He sells the butterflies for $3 each. How much money does he make? Let's think first. Chain of thought:
He has 4 * 10 = 40 caterpillars. 40 * .4 = 16 fail to form. That means he has 40 - 16 = 24 butterflies. So he makes 24 * 3 = $72.
Therefore, the answer is 72.