Two girls move in opposite directions, one from A to B and the other from B to A. The girl from A reaches the destination in 12 minutes. The girl from B stops on the way for 10 minutes and reaches her destination in 25 minutes. If A's speed is 5 km/h, then what is the speed of B?

Options

A. 3km/h
B. `1 5/7` km/h
C. 4km/h
D. 2.4 km/h

Answer

To solve the problem step-by-step, we will break down the information given and calculate the speed of the girl moving from B to A.

### Step 1: Understand the Information Given
- The girl from A to B takes 12 minutes to reach her destination.
- The girl from B to A takes 25 minutes in total but stops for 10 minutes on the way.
- The speed of the girl from A to B is 5 km/h.

### Step 2: Convert Time from Minutes to Hours
Since speed is given in km/h, we need to convert the time taken into hours.
- For the girl from A to B:
\[ \text{Time} = 12 \text{ minutes} = \frac{12}{60} \text{ hours} = \frac{1}{5} \text{ hours} \]

### Step 3: Calculate the Distance Between A and B
Using the formula for distance:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
For the girl from A to B:
\[ D = 5 \text{ km/h} \times \frac{1}{5} \text{ hours} = 1 \text{ km} \]

### Step 4: Analyze the Journey of the Girl from B to A
The girl from B to A takes a total of 25 minutes, but she stops for 10 minutes. Therefore, the actual time she spends moving is:
\[ \text{Moving Time} = 25 \text{ minutes} - 10 \text{ minutes} = 15 \text{ minutes} \]
Convert this to hours:
\[ \text{Moving Time} = \frac{15}{60} \text{ hours} = \frac{1}{4} \text{ hours} \]

### Step 5: Calculate the Speed of the Girl from B to A
Using the distance calculated earlier (which is 1 km), we can find the speed of the girl from B to A:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{1 \text{ km}}{\frac{1}{4} \text{ hours}} = 1 \text{ km} \times 4 = 4 \text{ km/h} \]

### Conclusion
The speed of the girl moving from B to A is **4 km/h**.

---