A and B are 20 km apart. A can walk at an average speed of 4 km/hour and B at 6 km/hr. If they start walking towards each other at 7 a.m., when they will meet ?

Options

A. 8.00 a.m
B. 8.30 a.m
C. 9.00 a.m
D. 10.00 a.m

Answer

To solve the problem of when A and B will meet, we can follow these steps:

### Step 1: Understand the speeds of A and B
- A walks at a speed of 4 km/hour.
- B walks at a speed of 6 km/hour.

### Step 2: Calculate the relative speed
Since A and B are walking towards each other, we can add their speeds to find their relative speed:
\[ \text{Relative Speed} = \text{Speed of A} + \text{Speed of B} = 4 \text{ km/hr} + 6 \text{ km/hr} = 10 \text{ km/hr} \]

### Step 3: Determine the distance between A and B
The distance between A and B is given as 20 km.

### Step 4: Calculate the time taken to meet
To find the time it takes for A and B to meet, we can use the formula:
\[ \text{Time} = \frac{\text{Distance}}{\text{Relative Speed}} \]
Substituting the values we have:
\[ \text{Time} = \frac{20 \text{ km}}{10 \text{ km/hr}} = 2 \text{ hours} \]

### Step 5: Determine the meeting time
Since A and B start walking at 7 a.m., we add the time taken to meet to the starting time:
\[ \text{Meeting Time} = 7 \text{ a.m.} + 2 \text{ hours} = 9 \text{ a.m.} \]

### Final Answer
A and B will meet at **9 a.m.**

---