I keep getting an answer that is similar to the correct answer... 12635.58 What am i doing wrong?

Connor deposited $842.38 in a savings account 15 years ago. The account earns 3.4% simple interest. What is his account balance today? (2 points)
X
$429.61

$871.02
✓
ANSWER : $1,271.99

$4,296.14

Question

I keep getting an answer that is similar to the correct answer... 12635.58 What am i doing wrong? 

Connor deposited $842.38 in a savings account 15 years ago. The account earns 3.4% simple interest. What is his account balance today? (2 points)
X		
$429.61
 	
$871.02
✓		
ANSWER : $1,271.99
 	
$4,296.14

welshfella · Answer

interest = P*R*T  / 100

welshfella · Answer

= (842.38 *3.4*15 )/ 100
then add this amount to the original principal $842.38

kaylaprincess · Answer

why divide by 100?

kaylaprincess · Answer

@welshfella

welshfella · Answer

because the rate is 3.4 per cent    which as a fraction is 3.4 / 100

kaylaprincess · Answer

thank you!
could you answer one more super easy question?

kaylaprincess · Answer

Liam deposited $1,724.53 in a savings account 4 months ago. The account earns 3.1% simple interest. What is his account balance today? 

I dont need help solving this, but when setting up the equation, what number what i put in for the time variable since simple interest is yearly?

kaylaprincess · Answer

im not sure if that question makes sense just let me know !

kaylaprincess · Answer

@welshfella