F.2 maths x2

1. The simple interest:
$20000*4%*2
=$1600
The compounded interest:
$20000*[1+4%]^(2) - $20000
=$1632
The difference
=$1632 - $1600
=$32

2. Ler r% be the simple interest rate
P*r%*20 = 3P
P*r% = (3/20)P
r% = 3/20
r% = 0.15
r = 15
(Therefore), the simple interest rate is 15%.

2007-08-22 23:24:01 補充：
係喎第三個答案講得岩我唔記得左加番P第二條係10%

( 1 ) In the case of simple interest:

$ 20000 x 4% x 2 = $ 1600

In the case of compound interest:

$ 20000 ( 1 + 4% )^2 - $ 20000

= $ 1632

The difference = $ 1632 - $ 1600 = $ 32

Hence the interest will be $ 32 more if it is compound interest.

( 2 ) Let the sum of money be $P and the rate be r%.

P + P x r% x 20 = 3P

1 + 1 x r% x 20 = 3

r% x 20 = 2

r% = 1 / 10

r = 10

Hence the rate is 10% p.a. to triple the sum of money in 20 years.


2007-08-22 14:56:39 補充：
The 1st one got question 2 wrong.

simple interest :

$20000 + (20000 x 4% x 2 )

= 20000 + 1600

= $ 21600.00

compound interest:


$20000 x (1+4%)squaer

= 20000 x 1.0816

= $21632.00


$21632 - $21600

= $32.00

第2題唔明...幫你唔到..