Question

You want to study at the Hogwarts School of Witchcraft and Wizardry after three years. You need 910910 pieces of muggle-money to study there. You decide to deposit some pieces in the bank at an annual interest rate of 10\%10%.
How many pieces should you deposit today if you want to use the total amount to pay the fees?

Answer 1

Answer:

You should deposit 700 pieces today if you want to use the total amount to pay the fees.

Step-by-step explanation:

Suppose, you should deposit $P$ number of pieces today.

Formula for simple interest:    $I= P*r*t$ , where I = Amount of interest, P= Initial deposit amount, r= rate of interest in decimal form and t= time duration.

Here, the $P$ number of pieces is deposited at an annual interest rate of  10% for three years. That means,  $r= 10\%= 0.10$ and $t= 3$

Using the above formula, we will get.......

$I= P*0.10*3 = 0.3P$

Given that, you need total 910 pieces of muggle-money to study after three years. So, the equation will be......

$P+I= 910\\ \\ P+0.3P=910\\ \\ 1.3P=910\\ \\ P=\frac{910}{1.3}=700$

So, you should deposit 700 pieces today if you want to use the total amount to pay the fees.