A student goes to school at a speed of 20 km/h and reaches 6 min late. If he goes at a speed of 30 km/h, he is 6 min early. What is the distance to the school?

Correct option is C

Given:

Speed when student reaches 6 min late = 20km/hr

Speed when student reaches 6min early = 30km/hr

Formula Used:

Distance=$$Speed \times Time$$​​

Solution:

Let the time taken to reach school when student goes at 20km/hr be t

Then

​$$20\times t = 30 \times (t-\frac{12}{60})$$​      (Distnace is constsant)

​$$20\times t = 30 \times (t-\frac{1}{5})$$​​

​$$20\times t = 30 \times (\frac{5t -1}{5})$$​​

​$$20\times t = 6 \times (5t -1)$$​​

​$$20t = 30t - 6$$​

​$$10t= 6$$​​

​$$t= \frac{6}{10}hr$$​

​$$Distance = 20\times \frac{6}{10} = 12km$$​​