a) 30 km and 42 km, after 6 hours

b) 27 km and 45 km, after 3 hours

c) 40 km and 32 km, after 4 hours

d) 52 km and 20 km, after 4 hours

correct answer is : c) 40 km and 32 km, after 4 hours

**Explanation**

Let the time will be ‘x’ hours when they meet each other.

We know,

Distance = speed\ \times\ time

Here, 1^{st} friend speeds are 10 km/hour.

\therefore Distance covered by 1^{st} friend is = \left(x\ \times\ 10\right) km

= 10x km.

And 2^{nd} friend speeds are 8 km/hour.

\therefore Distance covered by 2^{nd} friend is = \left(x\ \times\ 8\right) km

= 8x km

According the question,

\rightarrow\ 10x\ +\ 8x\ =\ 72 km

\rightarrow\ 18\ x\ =\ 72

\rightarrow\ x\ =\ \frac{72}{18}

\rightarrow\ x\ =\ 4

\therefore The time will be 4 hours when they meet each other.

And Distance covered by 1^{st} friend is = \left(10\ \times\ x\right) km.

= \left(10\ \times\ 4\right) km. _{[x = 4]}

= 40 km

And Distance covered by 2^{nd} friend is = \left(8\ \times\ x\right) km.

= \left(8\ \times\ 4\right) km. _{[x = 4]}

= 32 km **Ans:** They will meet 40 km from the starting point of the first friend and 32 km from the starting point of the second friend after 4 hours.