Correct Answer - Option 3 : 9 m

**Given:**

Two people are cycling at a speed of 10.8 km/hr and 12 km/hr, and in the same direction, a bus is also traveling. The bus crosses two people in 9 and 13.5 seconds.

**Formula used:**

Speed = Distance/ Time

**Calculation:**

Let us assume the speed of the Bus = B km/hr, L m be the length of the bus.

Now the distance traveled by two people while Bus crosses them is the length of the Bus.

⇒ (L) m = (B – 10.8) × 9 × 5/18 = (B – 12) × 13.5 × 5/18

⇒ (B – 10.8) × 9 = (B – 12)× 13.5

⇒ 2× (B – 10.8) = 3× (B – 12)

⇒ 2B – 21.6 = 3B – 36

⇒ 36 – 21.6 = 3B – 2B

⇒ B = 14.4 Km/hr

Now the length of the bus L m will be

∴ (14.4 – 12) × 13.5 × 5/18 = 9 m