Explanation:

- The bus was 60 minutes (1 hour) late but reached the destination on time. This implies it traveled faster.

- The distance to the destination is 48 km.

- The usual speed is \( x \) km/hr. The new speed is \( x + 4 \) km/hr.

- Equation for normal speed:

$$ \text{Time} = \frac{\text{Distance}}{\text{Speed}} = \frac{48}{x} $$

- Equation for increased speed:

$$ \text{Time} = \frac{48}{x + 4} $$

- The bus was late by 1 hour, so:

$$ \frac{48}{x} - \frac{48}{x + 4} = 1 $$

- Solving this equation:

- Multiply through by \( x(x + 4) \) to clear fractions:

$$ 48(x + 4) - 48x = x(x + 4) $$

- Simplifying gives:

$$ 192 = x^2 + 4x $$

- Rearrange to form a quadratic equation:

$$ x^2 + 4x - 192 = 0 $$

- Solve for \( x \) using the quadratic formula. Upon solving, the value of \( x \) is 12.

- Correct Answer:

Option 2: 12 km/hr