Question 1: Calculate the interest I if the principal P is $500, the rate R is 4%, and the time T is 3 years.

Answer: 60

Question 2: A principal of $1200 earns $180 interest in 2 years. What is the rate R?

Answer: 15

Question 3: If the interest I is calculated to be $45 for a principal of $900 over 3 years, what rate R was used?

Answer: 5

Question 4: A student mistakenly uses the formula I = P + R + T instead of I = PRT/100. What is the error in this calculation? Explain briefly.

Answer: They are adding the values instead of multiplying P, R, and T and dividing by 100.

Question 5: Plot the graph of I = (1/2) P R T/100 for P=100, R=10%, T=1 to 10 years.

Answer:

Question 6: Construct a triangle with sides proportional to the principal, rate, and time for a simple interest problem where P=200, R=5%, T=4 years. Label the sides accordingly.

Answer:

Question 7: A loan of $1500 earns interest of $90 in 3 years. What is the correct rate R? Show your working.

Answer: 2

Question 8: Identify the mistake in the following calculation: A principal of $800, rate 8%, time 2 years. Student calculates interest as 8 x 2 x 800 = 12800.

Answer: They forgot to divide by 100; the correct interest is (8 x 2 x 800)/100 = 128.

Question 9: A researcher states that increasing the rate R will always increase interest I, assuming P and T are constant. Is this statement always true? Justify your answer.

Answer: Yes, because I = PRT/100, so increasing R increases I proportionally.

Question 10: Calculate the interest if the principal is $1000, the rate is 7%, but the formula used is I = P R T/100 without proper parentheses. What mistake might occur?

Answer: Without parentheses, multiplication order is correct; but if the formula is misapplied or misinterpreted, students might forget to divide by 100, leading to an overestimation.