# Have I got these percentage calculations right with the math?

Disclaimer: These are hypothetical scenarios, not real.

In 1995, a Ford Mondeo costs £13,695 for a basic model.

In 2017, a Ford Mondeo costs £18,550 for a basic model.

To work out how much the price has gone up in those years, I did:

13,695/18,550 = 0.7383

18,550/13,695 = 1.3545

1.3545 / 100 = 35.45

The car has gone up by 35.45%.

Am I correct, or is my math wrong with working out a cost increase?

Second example:

In 2017, a Mercedes-Benz C-Class cost £24,650 for a basic model

In 1988, a Mercedes-Benz 190 cost £8,995 for a basic model.

These are my calculations:

24,650/8,995 = 2.7404

8,995/24,650 = 0.3649

The car has gone up by 174.04% in between.

Is my math correct, or do I need to correct my calculations for working out percentage increase or decrease?

• "1.3545 / 100 = 35.45", while the right result, is the wrong operation. What you really do here is subtract 1, and then rewrite from a decimal to a precentage (which essentially is multiplying by 100). So I would write it as "(1.3545 - 1) * 100 = 35.45", alternatively "1.3545 * 100 - 100 = 35.45" – Arthur Sep 14 '17 at 11:46

For calculating percentage increase or decrease the formula is $$\frac{y-x}{x} \times 100$$ where y is the new price and x is the old price. For your sums it would be $\frac{18,550 - 13,695}{13,695} \times 100 = 35.45 \%$ and $\frac{24,650 - 8,995}{8,995} \times 100 = 174.04 \%$