A student measured the length of a room and obtained the measurement of 3.99m. If the percentage error of is measurement was 5% and his own measurement was smaller than the length , what is the length of the room?
A. 3.78m B. 3.80m C. 4.18m D. 4.20m E. 4.788m
Correct Answer: D
Explanation
Let the actual length of the room = y m \(\therefore \frac{y - 3.99}{y} \times 100% = 5%\) \(100(y - 3.99) = 5y \implies 100y - 399 = 5y\) \(100y - 5y = 399 \implies y = \frac{399}{95}\) y = 4.2 m
