# Math Help - 2 questions

1. ## 2 questions

1 i have no clue how to do.. other somehwat...

first one...

2 student loans totalin 10,000.. he borrwed the max allowed at 7% simple interest and the remainder at 8.25% simple interest. After 1 year he owed 725 in interest.. how much did he borrow @ each interest rate

first i did 10,000 x .07 = 700
then 10,000 x .0825 = 825... but i dont know what to do, i dont think i did that step right

second problem

owned of video store sells 96 blank tapes per week if he charges 6 per tape. for every .50 he increases the price, he sells 4 fewer tapes per week.

i have to write equations for price / # of tapes / revenue

so woulnd't price = 6 + .5x
tape = 96 - 4x
revenue = (6 + .5x)(96 - 4x)

how mcuh should he charge for a tape in order to make a revunue of 630 per week from the tapes

any help is appreciated or point me in the right direction... thank you again!

2. Originally Posted by Ilovemath123
1 i have no clue how to do.. other somehwat...

first one...

2 student loans totalin 10,000.. he borrwed the max allowed at 7% simple interest and the remainder at 8.25% simple interest. After 1 year he owed 725 in interest.. how much did he borrow @ each interest rate

first i did 10,000 x .07 = 700
then 10,000 x .0825 = 825... but i dont know what to do, i dont think i did that step right
you have two equations here, where x is the "max" allowed and y is the "remainder"
x+y = 10,000
.07x+.0825y = 725

solve top for x and then plug into the second:
x = 10,000-y
.07(10,000-y)+.0825y = 725 ==> .0125y+700=725 ==> y=2,000

so then x+2000=10,000 ==> x=8,000

Originally Posted by Ilovemath123
second problem

owned of video store sells 96 blank tapes per week if he charges 6 per tape. for every .50 he increases the price, he sells 4 fewer tapes per week.

i have to write equations for price / # of tapes / revenue

so woulnd't price = 6 + .5x
tape = 96 - 4x
revenue = (6 + .5x)(96 - 4x)

how mcuh should he charge for a tape in order to make a revunue of 630 per week from the tapes

any help is appreciated or point me in the right direction... thank you again!
your equations here seem right to me. now all you would do is solve for x in the equation 630 = (6 + .5x)(96 - 4x). i got x = 3 or x = 9. so he could charge either $7.50 or$10.50 to make \$630 per week. the question doesnt say if the price or the tapes sold should be minimized or maximized, so either answer is right.