Make this lesson high interest and valuable by stressing its importance in the everyday world. Collect real life proof of the importance of using this skill (i.e. ads that show discounts, bank statements that show interest, receipts with tip or discount). Emphasize how important this skill is and challenge your child to find the best deals or earn the most interest while “window shopping”. You may also want to take a fieldtrip to the clearance section your child’s favorite store and calculate discount and sale price for the items found there.
Discounts are always subtracted from the original price to find a sale price. However, it is very important to note that some problems simply ask for the discount, not the sale price. The discount is simply the amount that will be taken off of the original amount. To find a discount you always use one operation, multiply. To find sale price you must first multiply to find the discount and then subtract that amount from the original price.
Remind your child of short cuts like: 50% off is ½ off so, just divide by two; 25% off is ¼ off so divide by 4; 10% off can be calculated by moving the decimal from the dollar amount one space to the left and re-writing this as the discount amount. 20% can be found by finding 10% and doubling it (multiply by 2).
Review the steps to change a percent into a decimal. To change a percent into a decimal you need to find the decimal point (if there is no decimal point it is assumed to be behind the last number before the percent sign) and move the decimal two spaces to the left. For example, 100% = 1.00, 65% = .65, and 1.25% = .0125.
Review the steps to find the percent of a number. Students will need to be able to do this in order to find a discount amount, tip or interest. For example, to find out what 15% of $60 is your student will need to change the percent into a decimal and then multiply the decimal by the dollar amount. So, .15 x 60 = $9.00.