Robert said
Bob bought two computers, one desktop and one laptop. Before finance charges, the laptop cost $1000 more than the desktop. Bob paid for the computers using two different financing plans. For the desktop the interest rate was 3% per year, and for the laptop it was $4.5 per year. The total finance charges for one year were $420 . How much did the desktop computer cost before finance charges?

Nicholas said
Let l be the cost of the laptop and d the cost of the desktopl=1000+d since the laptop cost $1000 more than the desktopfinance charge is f=(0.03)d + (0.045)l = 420I'm assuming here you meant the laptop had 4.5% finance chargessubstitute l=1000+d into f and solve for d(0.03)d + (0.045)(1000+d) = 4200.03d + 45 + 0.045d = 4200.075d + 45 = 4200.075d = 375d = 5000

Christian said
Bob bought two computers, one desktop and one laptop. Before finance charges, the laptop cost $1000 more than the desktop. Bob paid for the computers using two different financing plans. For the desktop the interest rate was 3% per year, and for the laptop it was $4.5 per year. The total finance charges for one year were $420 . How much did the desktop computer cost before finance charges?Let’s say the desktop cost d.The laptop cost d+1000, a thousand more.The interest rate on the desktop is 3%... so the interest over the year on the desktop was .03dThe interest rate on the desktop was 4.5%... so the interest over the year on the laptop was .045(d+1000).03d + .045(d+1000) = 420 (Given)Distributing in the second term we get.03d + .045d + 45 = 420Add -45 to each side….03d + .045d = 375Apply distributive property to the left side…(.03+.045)d=375Doing the arithmetic.075d = 375Multiplying both sides by 1/.075…d = 5000ALWAYS check you answer…(.03)d + (.045)(d+1000)=(.03)(5000) + (.045)(5000+1000)=150 + (.045)(6000)=150+270=420 IT CHECKS.

nathymasck said
ok the way you solve this problem is to start at the end and work your way backwards. you know that the charge for 1 year is $420, and you know what the percentages are so:420 = (laptop * 0.045) + (desktop * 0.03)you also know that the laptop costs $1000 more than the desktop so:laptop = desktop + 1000you can put these together and you get:420 = ((desktop + 1000) * 0.045) + (desktop * 0.03)distribute the 0.045 in the first bunch and you get:420 = (desktop * 0.045) + 45 + (desktop * 0.03)now you can mash the two desktop values together:420 = (desktop * 0.075) + 45from here it's simple algebra:375 = desktop * 0.0755000 = desktopso the desktop costs $5000 and the laptop costs $6000don't forget to plug those back into the initial problem to check it:420 = (laptop * 0.045) + (desktop * 0.03)420 = (6000 * 0.045) + (5000 * 0.03)420 = 270 + 150420 = 420

paramorearg said
desktop (d) cost x dollars the laptop (l) cost x+1000 dollarsd interest= .03x l interest = .045(x+1000)so .03x+.045(x+1000)= 420or ,03x+.045x+45=450or.075x=450-45.075x=405x=5400 desktop cost 5400laptop cost 6400assuming no compounded interest and $4.5 was a typo should have been 4.5% per year

Seth said
If you meant that the finance charge for the laptop was 4.5%, then you would answer it the following way:Let x = cost of desktopx+1000 = cost of laptop.03x + .045(x+1000) = 42030x + 45(x+1000) = 420,00030x +45x +45000 = 420,00075x = 375,000x=5000