Math Problem Solver

Answer: \(3\%\) Explanation: Step 1: Use the formula for simple interest \( S.I = \frac{P \times r \times t}{100} \), where \( P \) is the principal amount, \( r \) is the rate of interest, and \( t \) is the time in years.Step 2: Substitute the given values into the formula: \( 21 = \frac{280 \times r \times 2.5}{100} \).Step 3: Solve for \( r \) by multiplying both sides of the equation by \( \frac{100}{280 \times 2.5} \): \( r = \frac{21 \times 100}{280 \times 2.5} \).Step 4: Calculate the value of \( r \): \( r = \frac{2100}{700} = 3 \).Therefore, the rate of interest is \(3\%\).Explanation: Step 1: Use the formula for simple interest \( S.I = \frac{P \times r \times t}{100} \), where \( P \) is the principal amount, \( r \) is the rate of interest, and \( t \) is the time in years.Step 2: Substitute the given values into the formula: \( 21 = \frac{280 \times r \times 2.5}{100} \).Step 3: Solve for \( r \) by multiplying both sides of the equation by \( \frac{100}{280 \times 2.5} \): \( r = \frac{21 \times 100}{280 \times 2.5} \).Step 4: Calculate the value of \( r \): \( r = \frac{2100}{700} = 3 \).Therefore, the rate of interest is \(3\%\).