GCSE Trial & Improvement Questions - easy when you know how.

In ‘trial & improvement’ questions, there are steps you can use to guarantee full marks. The idea is to gradually zero in on a reasonable answer. A methodical approach is needed to gain a relatively easy 4+ marks.

Let’s look at an example…

Using the following equation, find a solution for x using a trial and improvement method

Give your answer to 1 decimal place.

To maximise your marks, you need to show step -by-step reasoning.

First, draw a table like this…

For x values, you are looking for two consecutive numbers between which the target number lies... We'll try x = 2 and 3

The target lies more towards x=3 value so it is reasonable to try x = 2.8 or 2.9

2.8 is too low - try 2.9…

So now we know the x lies between 2.8 and 2.9 but does it lie more to 2.8 or 2.9? Time for one last calculation to find out. Try a value halfway between these values… 2.85.

The value for x must be greater than 2.85, so the answer is…

x = 2.9 (to 1 d.p.)

Maximise the marks

• Draw a table (if it's not done for you!)

• Find two consecutive numbers so that the value for x lies between them (this may be given in the question)

• Make small, incremental adjustments to narrow the values - don’t ‘fly around’ using, say, 5 then 8 or 4.4 then 4.9.

• Examiners want to see a methodical, step-by-step approach to finding a value for x.