Question

The car arrives from city A to city B in 3 hours. How many hours will it take to go the same way if you increase the speed by 20%?

Answer 1

Given :-

• The car arrives from city A to city B in 3 hours.
• Speed is increased by 20% .

To find :-

• The new time taken .

Solution :-

Let us assume the distance between A and B be x and the initial speed by y . After 20% increase in the speed , new speed will be ,

$\blue{\dashrightarrow}$ Speed = 120y/100

$\blue{\dashrightarrow}$ Speed = 6/5y

• According to the Question ,

$\red{\dashrightarrow}$ Distance = Speed * Time

$\blue{\dashrightarrow}$ x = y * 3 hrs

$\red{\dashrightarrow}$ x = 3y

And ,

$\blue{\dashrightarrow}$ t = Distance/Speed

$\red{\dashrightarrow}$ t = x ÷ (6y/5)

$\blue{\dashrightarrow}$ t = 5x/6y

$\red{\dashrightarrow}$ t = 5 (3y)/6y

$\blue{\dashrightarrow}$ t = 5/2 hrs

$\red{\dashrightarrow}$ t = 2.5 hrs

Hence now it will take 2.5 hrs to go from A to B .

Answer 2

Answer:

Step-by-step explanation:

Let's say the distance between A and B is 3 miles (3, because I see a need to divide the distance by 3 hours to determine the car's speed).  The actual distance makes no difference in the answer, since it is asking for a relative speed change (20%).

We find the speed to be 3 miles/3 hours, or 1 mph.  A 20% increase in speed would be (1.20)(1) = 1.20 mph.

We can find the time for a 1.2 mph car to go 3 miles by:

(3 miles)/(1.2 mph) = 2.5 hours

=====

[Note that if we assumed a different distance, say 6 miles, we'd get the same result:

6 miles/3 hours = 2 mph

1.2*2 = 2.4 mph

New time = 6/2.4 = 2.5 hours; same as before]