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?
- 3.78m
- 3.80m
- 4.18m
-
4.20m
- 4.788m
The correct answer is: 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