Tag Archives: Steven Pinker

Can you solve this logic quiz?

Harvard cognitive psychologist Steven Pinker has a new book, Rationality, in which he makes the case that our gut instincts are often, if not always, wrong.

He used, as an example, what he calls a “simple logic” question:

A smartphone and case, combined, cost £110. The phone costs £100 more than the case. How much is the case?

What is your answer?

Scroll down for the correct answer.

If you answered £10, like most people you are wrong.

The correct answer is £5.

Here’s how I figured it out:

If X is smart phone, and Y is the case.

X+Y = £110

X = £100+Y

£110 = £100+2Y

Therefore Y = £5 and X = £100+£5 = £105