Problem No. 8. Seven 7s

How can you make 30, using seven 7s and the basic math operations (brackets are allowed)? What is the smallest number of 7s you can use, to make 30?

Parent tip

Have fun with your kids by exploring and calculating different number sentences. Do not forget that the brackets can help a lot.

Solution

There are several ways to make 30, using seven 7s. Here are some of them:

$$7 + 7 + 7 + 7 + (7 + 7) / 7 = 30,$$

$$(7 + 7 + 7 / 7) \cdot (7 + 7) / 7 = 30,$$

$$(7 - 7 / 7) \cdot (7 - (7 + 7) / 7) = 30.$$

Is there a smaller number of 7s that make 30?