JAMB Mathematics 2023 Paper

Amount (A) = Principal (P) + Interest (I) i.e. A = P + I

1 = $\frac{PTR}{100}$

A = 3P; T = 10 years (Given)

Since A = P + I

$\implies 3P = P + \frac{P \times 10 \times R}{100}$

$\implies 3P = P + \frac{10PR}{100}$

$\implies 3P = P + \frac{PR}{10}$

$\implies 3P - P = \frac{PR}{10}$

$\implies 2P = \frac{PR}{10}$

$\implies \frac{2P}{1} = \frac{PR}{10}$

$\implies$ PR = 20P

$\therefore$ R = 20%

Since the rate stays the same

A = 5P; R = 20%;T =?; A =P + I

$\implies 5P = P + \frac{p \times T \times 20}{100}$

$\implies 5P - P = \frac{2PT}{10}$

$\implies 4P = \frac{2PT}{10}$

$\implies 2P = \frac{PT}{10}$

$\implies$ PT = 20P

$\therefore$ T = 20 years