Problem 5: Guardian Puzzles

This week the 1729 Maths School was featured in the Guardian’s ‘Can you solve it’ column, a biweekly feature containing fun maths problems.

Here is one of the puzzles:

The Sick Sixth

I have four numbers, a, b, c, and d.

There are six ways to multiply two of these numbers together: ab, cd, ac, bd, ad, bc.

The values of five of these products (not necessarily in this order) are 2, 3, 4, 5 and 6.

What is the value of the missing sixth product?

Solve all the 1729 Guardian problems here