Answer:
y = 1%
Step-by-step explanation:
From the formula;
Interest; i = PRT/100
P = £5000
R = 10%
After 1 year, we have;
i = 5000 × 10 × 1/100 = £500
Amount is now; 5000 + 500 = £5500
Since interest rate is now y% every year after the first one, then;
After 2nd year;
i = (5500 × y × 1)/100
i = 55y
So amount is now;
5500 + 55y
After 3rd year, interest is now;
i = (5500 + 55y) × y × 1/100
i = 55 + 0.55y²
Amount is now;
(5500 + 55y) + (55 + 0.55y²)
Since she has £5610.55 after 3 years, then;
(5500 + 55y) + (55 + 0.55y²) = 5610.55
0.55y² + 55y + 5555 - 5610.55 = 0
0.55y² + 55y - 55.55 = 0
From quadratic formula, y = 1%
