Palash drives from City A to B at 40 km per hour and returns over the same road at 30 km per hour and spends 8 hours away from home including a one hour stop for lunch. What is the distance (in km) between City A and City B?

Let the distance between City A and City B be "D" kilometers.

Palash drives from City A to B at 40 km per hour, so the time taken for the first leg of the journey is D/40 hours.

He returns over the same road at 30 km per hour, so the time taken for the return journey is also D/30 hours.

He spends 8 hours away from home, including a one-hour stop for lunch. Therefore, the total driving time is 8 - 1 = 7 hours.

Now, we can set up an equation using the time formula (Time = Distance / Speed) for the total driving time:

(D/40) + (D/30) = 7

To solve for D, we can find a common denominator and then solve for D:

(3D/120) + (4D/120) = 7

Now, combine the fractions:

(7D/120) = 7

To isolate D, multiply both sides of the equation by 120/7:

D = (7 * 120) / 7

D = 120 kilometers

So, the distance between City A and City B is 120 kilometers. The answer is 120.