Question

a boy is running at a speed of p km/h to cover a distance of 1km. but due to the slippery ground, his speed is reduced by q km/h. if he takes 'r' hours to cover the same distance, then ?

1. 1/r = pq/ p + q

2. 1/r = p + q

3. 1/r = p-q

4. r = p-q

Answer 1

I think something is missing here,
total times taking by him during = r hrs

let t1 time take to cover 1 km with speed P km/h
then , t1 = 1/P

and t2 time taken to cover 1 km with speed q km/h
then,
t2 = 1/q
now , total time = r
then ,

1/P + 1/q = r

r = (P +q )/Pq

1/r = Pq/(P + q)
hence option (1) is correct ,

Answer 2

Answer:

C

Step-by-step explanation:   old speed is p km/h

so new speed will be  = p - q km/h

distance = 1 km

total time = r hours

so by formula : time = distance / speed

r = 1 / p - q

OR

1 / r = p - q