Question

a car moves with a speed of 40km/h for 15 minutes and then with a speed of 60km/h for the next 15 minutes. what is the total distance covered by a car​

Answer 1

case I : when car moves with speed of 40 km/hr for 15 minutes

==============================

here time t = 15 min = 15 min × 1hr / 60 min = 1/4 hr

speed = 40 km / hr

speed = distance / time

=> distance = speed × time = 40 × 1 / 4 = 10 km = d1 say

case II : when car moves with speed of 60 km/hr for next 15 minutes

==============================

here time t = 15 min = 15 min × 1hr / 60 min = 1/4 hr

speed = 60 km / hr .

distance = speed × time = 60 × 1/4 = 15 km = d2 say

Therefore ,

Total distance travelled

= d1 + d2 = 10 + 15 = 25 km

Answer 2

Appropriate Question

A car moves with a speed of 40 km/h for 13 minutes and then with a speed of 60km/h for the next 15 minutes.The total distance covered by the car is ?

a) 100 km

b) 25 km

c) 15 km

d) 10 km

Required Answer

25 km ${\huge{\purple{✓}}}$

Given

Let the time taken by the car for the first part of the journey be $\sf{t_L}$ = 15 minutes

Let the time taken by the car for the second part of the journey be $\sf{t_2}$ = 15 minutes

Let the speed of the car for the first part of the journey be $\sf{V_1}$ = 40km/h

Let the speed of the car for the second part of the journey be $\sf{V_2}$ = 60km/h

To Find

Total distance covered by the car.

Formula to be used

• Distance covered = Speed × Total time taken.
• 1 h = 60 minutes.

Solution

Let the distance covered by the car in the first part of the journey be $\sf{d_1}$

Let the distance covered by the car in the second part of the journey be $\sf{d_2}$

$\sf{t_1}$ = 15 minutes, i.e., 15 minutes $\sf{× \frac{1}{60}={1}{4}}h$

$\sf{t_2}$ = 15 minutes, i.e.,15 minutes $\sf{× \frac{1}{60}={1}{4}}h$

$\sf{d_1}$ = $\sf{V_1}$ × $\sf{t_1}$ = 40km/h $\sf{× \frac{1}{4}}h$

= 10 km

$\sf{d_2}$ = $\sf{V_2}$ × $\sf{t_L</p><p>2}$ = 60km/h $\sf{× \frac{1}{4}}h$

= 15 km

Total distance covered by the car = $\sf{d_1}$ + $\sf{d_2}$ i.e., 10km + 15km

= 25 km

Therefore,

${\large{\boxed{\rm{Option (B),is \: correct}}}}$ ${\huge{\blue{✓}}}$