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.