If N2,500.00 amounted to N3,50.00 in 4 years at simple interest, find the rate at which the interest was charged

Analyze the question: The amount is given as "N3,50.00", which is a typo. Since N2,500 is the principal and the amount must be larger, the intended figure is most likely N3,500.00.

Concept: For simple interest,

I = (P × R × T) / 100

and Amount = Principal + Interest.

Solution (using N3,500):

1. Interest = Amount − Principal = 3,500 − 2,500 = N1,000
2. Use I = PRT/100: 1,000 = (2,500 × R × 4) / 100 1,000 = 100R R = 10%

Check: 2,500 × 10 × 4 / 100 = N1,000, and 2,500 + 1,000 = N3,500. ✔

Note on the typo: If the amount were literally N350, it would be less than the principal, which is impossible for simple interest.

Answer: D. 10%

Tip: First find the interest (Amount − Principal), then rearrange to R = (I × 100) / (P × T). Always check that the amount is larger than the principal, since that can reveal typos like this one.