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: Option 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