1970: Handheld Calculator.

Viewed by teachers as a threat to one of the basic skills, the calculator wasn’t welcome in many classrooms when it first appeared.

If you’ve tried to figure out a tip, lately, you know the teachers were right. The first calculators cost around $400, or about $2350 in today’s terms, and all they could do was add, subtract, multiply and divide.

Now for $28.49 (on Amazon.com) you can buy a calculator that can do all that, as well as financial functions like amortization, bond, depreciation, and compound interest.  And teachers have something new to worry about: that students will be using technology to glide through higher math.