Three numbers have a mean of 6. One of them is 4, and the other two are equal to each other. What is each of the two equal numbers?

الشرح

Three numbers with a mean of 6 must total 18, and taking away the known 4 leaves 14 to be shared between the two equal numbers, so each one is 7. Answering 14 stops at the amount the pair share between them and forgets that this amount belongs to two numbers rather than one.