# Math help from the Learning Centre

This guide provides useful resources for a wide variety of math topics. It is targeted at students enrolled in a math course or any other Centennial course that requires math knowledge and skills.

## Multiple Rates of Discount  ### How to use the formulas?

Example: An item values at \$28 after discount. If a trade discounts series of 25%, 15%, and 10% were offered, find the original price.

What do we know? \$28 is value after discounts ⇒ this is the net price (N = \$28). There are multiple discounts (25% = 0.25, 15% = 0.15, 10% = 0.10).

What are we looking for? We are looking for the original price before discounts ⇒ find the list price. The original price was \$48.80.

## Multiple Rates vs Single Rate

### Why are the multiple discounts of 25%, 15%, and 10% not the same as 25% + 15% + 10% = 50%? Whereas the sum of discounts 50% of \$100 equals \$50.

To find the single rate from multiple rates. Use the formula.

d = 1 - (1 - 0.25)(1 - 0.15)(1 - 0.10) = 0.42625 or 42.625%