Question

A man walks from his house to his daughter's school at a speed of 3 km/hr and returns at a speed of 4 km/hr.If he takes 21 minutes for the diuble journey find the dustance between his house and school

Answer 1

first convert 3km/hand 4km/h into m/s

3km/h=5/6m/s

4km/h=10/9m/s

let distance be x

x/5/6=t1[time=distance/speed]

x/10/9=t2

t1 +t2=21

x/5/6+x/10/9=21

6x/5+9x/10=21

12x/10+9x/10=21

21x=210

x=10