Question
A car travels at three-fourths of
its original speed, taking 20 minutes more than the usual time to cover a given distance. Find the usual time the car takes to cover this distance.Solution
ATQ,
Let the usual speed of the car be '4s' km/h and the distance be 'd' km. Let the usual time taken by the car be 't' hours. Using the relation: 
Now, at three-fourths of the original speed, the speed becomes (3/4) × 4s = 3s The time taken at this speed: 
Substitute 'd' from equation (I):
Multiply both sides by 3: 4t = 3t+1 t = 1 So, the usual time taken by the car is 1 hour or 60 mins
What will come in place of the question mark (?) in the following series?
130, 158, 214, 298, ?, 550
What will come in place of (?) question mark in the given number series.
22, 23, 19, 28, ?, 37
8, 12, 20, 32, 52, ?, 136
5, 23, 18, 36, 31, ?
What will come in place of the question mark (?) in the following series?
3.5, 9.5, 27.5, 81.5, 243.5, 729.5, ?
144, 288, 96, 384, 76.8, ?
257, 399, 566, ?, 983, 1237
3 2 10 ? 17 16
66, 17, 81, ?, 100, -21
110, 112, 116, 122, 130, ?
