# Math Help - Investment rate

1. ## Investment rate

Karl wants to buy a $800 TV in 21 months. How much should he invest now at 20% simple interest to have the money in 21 months? Investment =$

whatis the necessary equation?

thx

2. Originally Posted by makaveli89
Karl wants to buy a $800 TV in 21 months. How much should he invest now at 20% simple interest to have the money in 21 months? Investment =$

whatis the necessary equation?

thx
Interest= (Principal x %Rate per year x Time)/100
Here principal is the amount invested
If your time is in months divide it by 12
Principal + interest = amount ($800) 3. i don't get it. can u please go more into detail. i tried as equation: 1.2x^1.75 = 800 but it doesnt work, i guess its wrong. 4. ## I think this might be helpful......... Originally Posted by makaveli89 Karl wants to buy a$800 TV in 21 months. How much should he invest now at 20% simple interest to have the money in 21 months?
Investment =?
800=Investment+Interest

$Interest=\frac{Investment*21*20}{12*100}$

5. i dont know if this makes sense. i have no clue how to solve this

6. 1-"Money" has to be invested in the bank to get a profit at the rate of 20% annually this "Money " is called investment and the profit is called interest and the value that you need to get is amount (800$) 2- according to your question you need to get 800$ after 21 months at the rate of interest (20% per annum)

3-The formula used here is

$Interest=\frac{Investment*Months*\text {Rate of interest}}{12*100}$

$Amount= Investment+Interest$

Now which point you dont get? or is it the fourth option

4)All of these

7. what is the final equation?

this one

which is, 20 = 21*0.2*x / 12*100

????
is that correct because i think its wrong cause the result is not correct.