Read the information given carefully and answer the question that follows:
(A) 72 kmph = 20 m/s
(B) 25 m/s = 80 kmph
(C) Total Surface area of a Cube of edge length a is \(6a^2\)
(D) Volume of a Cube of edge length a is \(a^3\)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (C) & (D) only
To change km/h into m/s, multiply by \(\frac{1000}{3600}=\frac{5}{18}\) (1 km = 1000 m and 1 hour = 3600 s); to change m/s into km/h, multiply by \(\frac{18}{5}\).
(A) 72 kmph = 20 m/s Correct. \(72\times\frac{5}{18}=20\) m/s.
(B) 25 m/s = 80 kmph Incorrect. \(25\times\frac{18}{5}=90\), so 25 m/s is 90 km/h, not 80 km/h.
(C) Total Surface area of a Cube of edge length a is \(6a^2\) Correct. A cube has six square faces, each of area \(a^2\).
(D) Volume of a Cube of edge length a is \(a^3\) Correct. Volume is length × breadth × height, and all three are \(a\).