Also known as:
A simple mathematical, logical puzzle. Given the total values for several combinations of typically four objects, you are required to calculate the value of each individual object. It is not necessary to guess, or use trial and error. The best approach is to express this puzzle in terms of simple algebra.
For example, consider this problem:
If we think of the pebble as a, the sea urchin as b, the starfish as c and the seashell as d, then:
If 2a+2c=£18, then a+c=£9. This means that £9+b+d=£26, so b+d=£17. From here (see 2a+b+d=£23) the answer is easy to calculate.
Another common version of this puzzle is called Weighed Up. Here, the solver is given several pictures showing how various combinations of objects balance one another, and is required to calculate how many of a particular object will be required to make a final set of objects balance.