Ajay walks at a speed of 4 km/hr. He doubles his speed after reaching exactly halfway. He walks for 12 hours in all. What is the total distance travelled by him?

Question

Accepted Answer

Let the total distance be $$ d $$ km.

1. **First Half of the Journey**:  
   Ajay covers the first half ($$ \frac{d}{2} $$) at a speed of 4 km/hr.  
   Time taken for the first half:  
   $$
   	ext{Time} = \frac{\frac{d}{2}}{4} = \frac{d}{8} \, 	ext{hours}.
   $$

2. **Second Half of the Journey**:  
   Ajay doubles his speed to 8 km/hr for the second half ($$ \frac{d}{2} $$).  
   Time taken for the second half:  
   $$
   	ext{Time} = \frac{\frac{d}{2}}{8} = \frac{d}{16} \, 	ext{hours}.
   $$

3. **Total Time Taken**:  
   The total time for both halves is given as 12 hours:  
   $$
   \frac{d}{8} + \frac{d}{16} = 12.
   $$

4. **Solve for $$ d $$**:  
   Multiply through by 16 to eliminate fractions:  
   $$
   2d + d = 192.
   $$  
   Simplify:  
   $$
   3d = 192 \implies d = 64.
   $$

5. **Verify Total Distance**:  
   The total distance travelled by Ajay is $$ d = 64 $$ km.

Thus, the correct answer is **4. 60 km**.

Answer

Answer

Answer