Answer:
see explanation
Step-by-step explanation:
Her error is in squaring (2y)²
She has (2y)² = 2y²
when it should be 2y × 2y = 4y²
Then
(2y)² = 6² + 8²
4y² = 36 + 64
4y² = 100 ( divide both sides by 4 )
y² = 25 ( take square root of both sides )
y = = 5
Given:
Principal value = $640
Rate of interest = 3.9% not compounded
Number of years = 8
To find:
The amount after 8 years.
Solution:
It is given that the interest is not compounded. It means, we need to find simple interest.
Formula for simple interest:
where, P is principal, r is rate of interest and t is time in years.
Put P=640, r=0.039 and t=8.
So, the interest is $199.68.
Now, amount after 8 years is
where, P is principal and I is interest.
Therefore, the amount after 8 years is $839.68.
