If 5% of a number is £100,000, how much is the number?   A quick solution is to divide 100 by the percentage and multiply the number by this answer.  So in this case 100/5 = 20, so the entrepreneur thinks his business is worth 20 x £100,000 or £2,000,000.

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“This brings me on to one of the key points I have learned in business over the last few years. It is really crucial that Entrepreneurs understand percentages. That is the relationship between numbers. You need to see how a 1% fall in sales will affect your profit and hence your valuation (in the above case the relationship is 3 – a 1% fall in sales led to a 3% fall in profits). It is never straightforward.”

“Nothing beats one-to-one tuition for boosting a child’s performance,” says Susan Fieldman, regional editor of The Good Schools Guide. “State schools have 30 or more in a class and even private ones have 15.”

Demand is greatest for GCSE and A-level tutoring but the biggest area of growth is in the primary sector, especially among parents who are hoping to get their children into a grammar school.

The most popular subject at all levels is maths, followed by English, with parents typically hiring a tutor for a couple of terms prior to an important exam. Anita Moss, founder of the Bright Tutors agency, says: “It’s better to go for one hour a week spread across a year than cram, cram, cram.” A realistic aim is to go one grade better than the predicted mark based on mocks.

Does the formula P(1+r)n mean anything to you? Unless you are a mathematician, the answer is probably no, and yet of all mathematical equations, it is arguably the most important to our daily lives because banks use it to determine how much we should receive on our savings and how much we owe on our debts.

It is the formula for basic compound interest, where P stands for principle, or the amount of capital, r is the interest rate and n is the number of years. Mercifully, most of us never have to use it because the banks do the calculation for us.

However, experts say that a grasp of more basic mathematics is key to managing money, and if taught as part of personal finance in schools, it could help to erode the UK’s £1.4 trillion debt mountain.