#### Question

1) a dress is priced at \$21.42 . The store is having a 30%-off sale. What was the original price of the dress?

2) A man paid the bank \$4,080 at the end of 3 years. This was the amount borrowed plus 12% interest for 3 years. How much money ha he borrowed?

3) how many years will it take \$1,000 invested at 7% interest to earn \$280?

1) assume that x is the original prize

if the item is 30% off then it is selling for 70% of its original prize (because if the total percentage is 100% sales percentage would be 100% - 30%)

x * (70 / 100) = 21.42

x = 21.42* (100 / 70)

x = 30.6

2) first find the amount of interest that is in 4080

4080 * (12/100) = 489.6

then the amount of money borrowed would be = total - interest

= 4080 - 489.6

= 3590.4

3) if 7% interest is per year then first find the interest earned per year and divide it by 280 to find the number of years

1000 * (7/100) = 70

number of years = 280 / 70 = 4

hope this helps

#1

The original price is p , then (p -0.30 p) = 21.42

0.70p=21.42

p=21.42/0.70= \$30.60

Simple interest , Borrowed K , then K +12%K = 4.080

1.12K= 4.080

K=4.080/1.12 =\$3642.86

Simple interest 7% (n years ) *1000 = \$280

70 n=280

n=280/70=4 years

Compound interest K(1 +0.07)^n = Kf

earn , E = Kf - K

E= K(1+0.07)^n -K

E= K ( ( 1.07)^n -1)

1+ 280/1000 = 1.07^n

1.07^n =1.28

n log 1.07 = log1.28

n= log1.28/ log 1.07 =3.6486 years

( 3 years plus 7 month plus 23 days plus 12 hours )

( just in case ^_^)

#2

X - (.30*X)= 21.42 ---X is you original price. 30% of original X minus original which is X

X - .3X = 21.42

(1/1)X - .(3/1)X = 21.42---combine the X's

.7X = 21.42---divide both sides by .7

X=30.6---the original price of the dress was \$30.60

#3

dress q: 30 over 100 equals 21.42 over x, cross multiply and solve that because 30 is over 100 cuz of the 30 percent, 21.42 is over x because 21.42 is the sale price, over the regular price.

2nd: i think its i=prt, interest=principle times rate times time so 4080=p times 0.12 times 3 cuz 4080 is the total interest, principle i think is how much u borrowed, interest is obviousely the interest rate and 3 years, if its in months then u dont make it a fraction, its still like 4 for 4 months or watever

3rd: 1280=1000 times 7 times time so just make the t for time stand alone

and no, no answer cuz like evry adult that didnt help ME said i wont be there on the test

#4

look on the internet......

#5