This video is all about tangent proof - where a line touches a circle, and is aimed at GCSE maths grade 8. The whole idea is that it can be treated in a similar way to solving quadratic simultaneous equations, by substitution, but in this case there is only a single point. Prove algebraically that the straight line with the equation x - 2y = 10 is a tangent to the circle … [Read more...]

## Reverse percentage – prices in a sale

Reverse percentage are very popular GCSE maths problems, aimed at around grade 5. They are usually either percentage decrease - working out the normal price, if you know the sale price of an item - or percentage increase, such as property prices. Here's the questions, which are fairly representative of the types of reverse percentage questions usually asked: 1. In a sale, … [Read more...]

## Quadratic simultaneous equations – solving by substitution

These questions are fairly challenging and aimed at around grade 8 GCSE maths. They deal with solving quadratic simultaneous equations by substitution, and you'll need good 'algebra confidence.' Please do stop the video, try the questions and compare your solution. Video one - solve: x - 2x = 3 x² + y² = 18 Video two - solve: x - 2y = 1 x² + y² = … [Read more...]

## Finding the missing angle

These videos are examples of the 'finding the missing angle' types of questions. They can be a little challenging, although I hope that the examples will give you an overview of the range of GCSE maths problems. Unfortunately there isn't really a specific topic; these problems are more about solving. You might need circle theorems, and also properties of regular polygons - … [Read more...]

## Compound interest – growth and decay

These videos are examples of compound interest type questions - now called 'growth and decay.' George invested £3200 in a savings account for 3 years. He was paid compound interest at a rate of 3.5% per annum. Work out how much was in the account after 3 years? Tony invested £4500 for 3 years. He was paid 4% per annum compound interest. Calculate the total … [Read more...]