Correct Answer - Option 4 : 1600 km

**Given: **

Speed of the express train = 70 km/hr

Speed of the Rajdhani train = 90 km/hr

**Concept:**

In these types of questions, we find the time when they meet with the help of relative speed concept and then we find the distance between Delhi and Mumbai.

**Formula: **

Relative speed = S_{1 }+ S_{2 }(when trains move in the opposite direction)

Relative speed = S_{1 }– S_{2 }(when trains move in the same direction)

Distance = speed × time

**Calculation: **

let the time when they meet be x hrs

According to the question,

The faster train travels 200 km more than slower train

⇒ 200 = (90 – 70) × x

⇒ x = 200/20 = 10 hrs

Distance travelled by trains in 10 hrs = (90 + 70) × 10

= 1600 km

∴ Distance between Delhi and Mumbai = 1600 km