Speed, Time and Distance
- To cover a distance of 216 km in 3.2 hours, what should be the average speed of the car in metre/second?
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Required speed of car = Distance Time = 
216 
kmph. 3.2 = 216 × 5 m./sec. 3.2 18
= 18.75 m./sec.Correct Option: D
Required speed of car = Distance Time = 216 kmph. 3.2 = 216 × 5 m./sec. 3.2 18
= 18.75 m./sec.
- In covering a certain distance, the speed of A and B are in the ratio of 3 : 4. A takes 30 minutes more than B to reach the destination. The time taken by A to reach the destination is :
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Let the distance of destination be D km
Let the speed of A = 3x km/hr
then speed of B = 4x km/hr
∴ According to question,D − D = 30 minutes 3x 4x = 1 hr 2 ∴ D = 1 12x 2 ⇒ D = 4 = 2 hours 3x 2
Hence, time taken by A to reach
destination = 2hrs.
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 30 = y + 1 60 2
S1t1 = S2t23x × y + 1 = 4 x × y 2 3y + 3 = 4y 2 y = 3 2 ∴ Time taken by A = 3 + 1 = 2 hrs. 2 2 Correct Option: C
Let the distance of destination be D km
Let the speed of A = 3x km/hr
then speed of B = 4x km/hr
∴ According to question,D − D = 30 minutes 3x 4x = 1 hr 2 ∴ D = 1 12x 2 ⇒ D = 4 = 2 hours 3x 2
Hence, time taken by A to reach
destination = 2hrs.
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 30 = y + 1 60 2
S1t1 = S2t23x × y + 1 = 4 x × y 2 3y + 3 = 4y 2 y = 3 2 ∴ Time taken by A = 3 + 1 = 2 hrs. 2 2
- In covering a certain distance, the speed of A and B are in the ratio of 3 : 4. A takes 30 minutes more than B to reach the destination. The time taken by A to reach the destination is :
-
View Hint View Answer Discuss in Forum
Let the distance of destination be D km
Let the speed of A = 3x km/hr
then speed of B = 4x km/hr
∴ According to question,D − D = 30 minutes 3x 4x = 1 hr 2 ∴ D = 1 12x 2 ⇒ D = 4 = 2 hours 3x 2
Hence, time taken by A to reach
destination = 2hrs.
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 30 = y + 1 60 2
S1t1 = S2t23x × y + 1 = 4 x × y 2 3y + 3 = 4y 2 y = 3 2 ∴ Time taken by A = 3 + 1 = 2 hrs. 2 2 Correct Option: C
Let the distance of destination be D km
Let the speed of A = 3x km/hr
then speed of B = 4x km/hr
∴ According to question,D − D = 30 minutes 3x 4x = 1 hr 2 ∴ D = 1 12x 2 ⇒ D = 4 = 2 hours 3x 2
Hence, time taken by A to reach
destination = 2hrs.
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 30 = y + 1 60 2
S1t1 = S2t23x × y + 1 = 4 x × y 2 3y + 3 = 4y 2 y = 3 2 ∴ Time taken by A = 3 + 1 = 2 hrs. 2 2
- The speed of A and B are in the ratio 3 : 4. A takes 20 minutes more than B to reach a destination. In what time does A reach the destination ?
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Ratio of speed = 3 : 4
Ratio of time taken = 4 : 3
Let the time taken by A and B be 4x hours and 3 x hours respectively.Then, 4x–3x = 20 ⇒ x = 1 60 3
∴ Time taken by A = 4x hours= 4 × 1 hours 3 = 1 1 hours 3
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 20 = y + 1 60 3
S1t1 = S2t23x y + 1 = 4xy 3 ∴ Time taken by A = 1 + 1 = 1 1 hours 3 3 Correct Option: A
Ratio of speed = 3 : 4
Ratio of time taken = 4 : 3
Let the time taken by A and B be 4x hours and 3 x hours respectively.Then, 4x–3x = 20 ⇒ x = 1 60 3
∴ Time taken by A = 4x hours= 4 × 1 hours 3 = 1 1 hours 3
Second Method :
Here, S1 = 3x, S2 = 4xt2= y, t1 = y + 20 = y + 1 60 3
S1t1 = S2t23x y + 1 = 4xy 3 ∴ Time taken by A = 1 + 1 = 1 1 hours 3 3
- The ratio of length of two trains is 5 : 3 and the ratio of their speed is 6 : 5. The ratio of time
taken by them to cross a pole is
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Required ratio
= 5 : 3 = 30 × 5 : 30 × 3 6 5 6 5
= 25 : 18Correct Option: C
Required ratio
= 5 : 3 = 30 × 5 : 30 × 3 6 5 6 5
= 25 : 18
