1) A man can complete a journey in 10 h. He travels
first half of the journey at the rate of 21 km/h and
second half ot the rote of 24 km/h. Find the total
journey in km.
2) A truck completes a journey of 300km in 7 1/2 hour and the bus covers a journey of 450 km in 9 hour. find the ratio of their speeds
3) An aeroplane covers a certain distance at a speed of 240km/h in 5 hr. to cover the same distance in 1 2/3 hr, it must travel at a speed of?
Answers
Answer:
224 km
Step-by-step explanation:
1)Distance = Speed × Time
METHOD - 1 :
Total Journey made = 10 Hrs
Let total distance be d Km
First half of the distance /frac{d}{2}/fracd2 travelled at 21 kmph in x hrs
=> d/2 = 21xd/2=21x
=> d = 42xd=42x --------(1)
Second Half of the distance (d/2) travelled at 24 kmph in (10-x) Hrs
=> \frac{d}{2} = 24 × (10 - x)
2
d
=24×(10−x)
=> d = 48(10 - x)d=48(10−x)
=> x = 10 - (\frac{d}{42})x=10−(
42
d
) -------(2)
From eq(1) & eq(2)
=> \frac{d}{42} = 10 - (\frac{d}{48})
42
d
=10−(
48
d
)
=> \frac{d}{42} + \frac{d}{48} = 10
42
d
+
48
d
=10
=> d = \frac{2×5×2×3×7×8}{3×5}d=
3×5
2×5×2×3×7×8
=> d = 224 Kmsd=224Kms
•°• Required distance covered = 224 km
•°•°•°•°•°<><><<><>><><>°•°•°•°•°•
Method -2 : Using Formula
¶¶¶ Suppose a man covers a certain distance at x kmph and an equal distance at y kmph.
Then,
The average speed during the whole journey is \frac{2xy}{x+y} kmph
x+y
2xy
kmph
Given, x = 21 y = 24
Average speed = \frac{2×21×24}{21+24}
21+24
2×21×24
Distance = speed × time = 22.4 × 10 = 224 km
2)Check the attachments
3)
Distance = (240 × 5) = 1200 km.
Speed = Distance/Time
Speed = 1200/(5/3) km/hr. [We can write 1
3
2
hours as 5/3 hours]
∴ Required speed = (1200×
5
3
) km/hr=720 km/hr.
the 1st , 2nd were from brainly n the 3rd was from toppr
anyways
Hope it helps you
