Time: - The duration spent to cover a certain distance. [Unit - hr, min, sec]
Distance: - The length of the path travelled by an object between two places. [Unit – km, m]
Relationship between Speed, Time & Distance
Speed= Distance/Time
2) 1 km/hr = 5m/18s
Speed= Distance/Time
Example: - A car covers 10 miles in 4 hrs. Find the speed of the car?
5 miles= 8 km
So, 10 miles= 16km
speed= 16/4 - 4 km/hr
D1/T1 = D2/T2
Example: -A person covers km in 4 4/7 hrs. What distance will he cover in 7 hrs?
Avg. Speed= 2AB/A+B
Example: - Ruchi covers a distance from her home to school by car at 25 km/hr and she returns back by scooter with a speed of 20 km/hr. Find the average speed for the whole journey?
Example: - If Raju and Ravi travels from P to Q having the distance of 35 km at 8 km/hr and 6 km/hr respectively. Raju reaches Q first and returns immediately & meet Ravi at R. Find the distance travelled by Raju and Ravi?
Distance travelled by Raju = 2 ✕35 ✕ 8/14 = 40 km
Distance travelled by Ravi = 2✕35✕ 6/14= 30km
Example: - Richa went out to cycle from P to Q and at the same time Pooja starts to cycle from Q to P. After passing each other, they complete their journey in 16 hrs and 9 hrs respectively. If speed of the Richa is 27 km/hr then what will be the speed of Pooja?
Example: - Paresh increases his speed by times of his original speed and reaches his office at 20 minutes before the fixed time. Find the usual time taken by him?
Note: -
1) Unit of speed, time and distance should be in the same metric system.2) 1 km/hr = 5m/18s
Formulas Including Short Tricks:
Trick 1.
Calculation of Speed when units are not belong to same metric system –Speed= Distance/Time
Example: - A car covers 10 miles in 4 hrs. Find the speed of the car?
5 miles= 8 km
So, 10 miles= 16km
speed= 16/4 - 4 km/hr
Trick 2.
Calculation of distance if speed is constant –D1/T1 = D2/T2
Example: -A person covers km in 4 4/7 hrs. What distance will he cover in 7 hrs?
Trick 3.
Calculation of average speed if certain distance is covered at speed A & same distance is covered at distance B –Avg. Speed= 2AB/A+B
Example: - Ruchi covers a distance from her home to school by car at 25 km/hr and she returns back by scooter with a speed of 20 km/hr. Find the average speed for the whole journey?
Trick 4.
Calculation of distance if two persons travels from point P to Q ( having distance D) with given different speeds and second person reaches point Q first, returns immediately and meet first person at R –
Example: - If Raju and Ravi travels from P to Q having the distance of 35 km at 8 km/hr and 6 km/hr respectively. Raju reaches Q first and returns immediately & meet Ravi at R. Find the distance travelled by Raju and Ravi?
Distance travelled by Raju = 2 ✕35 ✕ 8/14 = 40 km
Distance travelled by Ravi = 2✕35✕ 6/14= 30km
Trick 5.
Calculation of speed if two persons start running at the same time in opposite direction (P & Q) between two points and after passing each other (R), they complete their journey in x and y hr respectively –
Example: - Richa went out to cycle from P to Q and at the same time Pooja starts to cycle from Q to P. After passing each other, they complete their journey in 16 hrs and 9 hrs respectively. If speed of the Richa is 27 km/hr then what will be the speed of Pooja?
Trick 6.
Calculation of time if a person changes his speed (in fraction such has times) of his original speed and reaches either late or early by t minutes –
Example: - Paresh increases his speed by times of his original speed and reaches his office at 20 minutes before the fixed time. Find the usual time taken by him?
