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Ex. 1) A color laser printer marked originally priced at $699 goes on sale for 30% off. If Chris has already saved up $325, how much more money does he need to buy the printer at the sale price? Find the discount. % part 100 whole 30 x 100 $699 20970 100x $209.70 x Find the sale price. Find how much more money Chris needs. Sale price = original – discount Sale price = $699 - $209.70 Sale price = $489.30 Money needed = sale price – money saved Money needed = $489.30 - $325 Money needed = $164.30 Ex. 2) A bicycle helmet is priced at $18.50. If it is on sale for 10% off and there is 7% sales tax, how much will it cost after tax? First, find the sale price at 10% off of the original price. 10 discount 100 original 10 x 100 $18.50 185 100x $1.85 x Sale price = original – discount Sale price = $18.50 – $1.85 Sale price = $16.65 Next, find the sale price plus 7% tax. 7 t ax 100 sale price 7 x 100 $16.65 116.55 100x $1.17 x Total cost = sale price + tax Total cost = $16.65 - $1.17 Total cost = $17.82 Ex. 3) All appliances at Bargain Outlet are marked down to 70% of the original price. Fred has a coupon for an additional 18% off of the sale price. If the original price of a microwave is $500, how much would Fred pay for the oven before tax? First, find the price at 70% off the original price. Next, find the price with the additional 18% off the sale price. 70 sale price 100 original 18 discount 100 sale price 70 x 100 $500 18 x 100 $350 35000 100x 6300 100x $350 x The final price is the sale price minus the additional discount. $62 x Final price = sale price – discount Final price = $350 - $63 Final price = $287 Ex. 4) Bob offered the salesperson at Furniture Express $600 for a new couch. This offer included 8% sales tax. If the salesperson accepts the offer, what was the cost of couch to the nearest dollar? The total cost of the couch plus tax is $600 . Let x = the cost of the couch The tax on the couch is 8% of the cost. 8 ( x ) 0.08 x 100 Total cost = cost of couch + tax $600 = x + 0.08x $600 = 1.08x $555.56 = x $556 ≈ x To the nearest dollar, the couch costs $556. Ex. 5) Between noon and 8:00 p.m., the temperature dropped from 70o F to 35o F. What was the percent decrease in temperature between noon and 8:00 p.m.? Remember, percent of change (increase or decrease) is a variation of the percent proportion. % change amountof change 100 original x 70 35 100 70 70x 100(35) 70x 3500 x 50% There was a 50% decrease in temperature between noon and 8:00 p.m. Ex. 6) The radius of a circle was estimated at 15.6 cm. The actual radius was 15.3 cm. Find the percent error in the estimation to the nearest hundredth of a percent. Percent error is another variation of the percent proportion. % error amount of error 100 actual x 15.6 15.3 100 15.3 15.3x 100(0.3) 15.3x 30 x 1.96% The percent error of the estimation was 1.96%. Ex. 7) What is the amount of simple interest on a principal of $580 invested at a rate of 7.5% for 3 years? The simple interest formula is I = prt where I = interest P = principal, or the amount of money borrowed or invested r = annual interest rate expressed as a decimal t = time in years I prt 7.5 I ($580) (3) 100 I ($580)(0.075)(3) In 3 years, $130.50 would be earned in simple interest. I $130.50