Aptitude - Time and Distance - Discussion
Discussion Forum : Time and Distance - General Questions (Q.No. 10)
10.
A car travelling with 
of its actual speed covers 42 km in 1 hr 40 min 48 sec. Find the actual speed of the car.
of its actual speed covers 42 km in 1 hr 40 min 48 sec. Find the actual speed of the car.
Answer: Option
Explanation:
| Time taken = 1 hr 40 min 48 sec = 1 hr 40 | 4 | min = 1 | 51 | hrs = | 126 | hrs. |
| 5 | 75 | 75 |
Let the actual speed be x km/hr.
| Then, | 5 | x x | 126 | = 42 |
| 7 | 75 |
 x = |
 |
42 x 7 x 75 |  |
= 35 km/hr. |
| 5 x 126 |
Discussion:
117 comments Page 2 of 12.
Vijay said:
3 years ago
Thanks @Siddharth.
(4)
Some people said:
3 years ago
How come 126? Please explain.
(11)
KUMARI SUPRITA said:
3 years ago
1hr + 40min + 48sec = 1 + (40/60) + (48/60*60).
= 1 + 2/3 + 1/75 = 126/75.
= 1 + 2/3 + 1/75 = 126/75.
(28)
Sree ezhil said:
4 years ago
Simple method:
S1: covert seconds to minutes
48/60 =0.8min ; 40min+0.8min =40.8min.
S2: convert min to sec.
40.8/60 =0.68 ; 0.68hr+1hr= 1.68hr
S3: for avg speed
5/7 x= 42/1.68,
5/7x = 25,
x = 25 * 7/5,
x = 35.
Hope you guys understand easily.
S1: covert seconds to minutes
48/60 =0.8min ; 40min+0.8min =40.8min.
S2: convert min to sec.
40.8/60 =0.68 ; 0.68hr+1hr= 1.68hr
S3: for avg speed
5/7 x= 42/1.68,
5/7x = 25,
x = 25 * 7/5,
x = 35.
Hope you guys understand easily.
(84)
Imtiaz said:
4 years ago
To convert the time 1 hr 40 min 48 sec to hours,
Hours = 1 + (40 ÷ 60) + (48 ÷ 3600),
Hours = 1 + 0.67 + 0.0134.
Hours = 1.68 hrs, which is nothing but 126/75.
Hours = 1 + (40 ÷ 60) + (48 ÷ 3600),
Hours = 1 + 0.67 + 0.0134.
Hours = 1.68 hrs, which is nothing but 126/75.
Avi said:
4 years ago
Isn't Time = Distance/Speed why did they multiply?
Also explain the step : 5/7x*75/126.
Also explain the step : 5/7x*75/126.
(1)
Poojith said:
4 years ago
1hr 40min and 48sec == 1.68hours.
5x/7 = 42/1.68,
5x/7 = 25.
5(25)/7 = 35km/hr.
5x/7 = 42/1.68,
5x/7 = 25.
5(25)/7 = 35km/hr.
(2)
Kalaiyarasan said:
4 years ago
Time taken = 1hr 40min 48sec.
= 1hr 40*4/5 min =1 * 17/25hr = 17/25 hr.
Time = 42/25 hr ,
Actual speed = 5/7 * x,
distance=42.
s = d/t.
5/7 * x = 42 * 25/42
x = 25 * 7/5,
x = 35km/hr.
= 1hr 40*4/5 min =1 * 17/25hr = 17/25 hr.
Time = 42/25 hr ,
Actual speed = 5/7 * x,
distance=42.
s = d/t.
5/7 * x = 42 * 25/42
x = 25 * 7/5,
x = 35km/hr.
Sandeep said:
5 years ago
Yes, as we all know that SPEED=DISTANCE/TIME.
Here they gave in hours so we have to convert entire to hours then we got 126/75 as time
And let us assume actual speed = x.
5/7 of speed = 5x/7.
Distance = 42,
By applying in the formula
Speed =distance/time.
5x/7 = 42/126/75,
5x/7 = 75 * 42/126 ,
Then we go 5x/7 = 3150/126.
While Criss cross we got,
630x = 22050,
X = 35km/hr.
Here they gave in hours so we have to convert entire to hours then we got 126/75 as time
And let us assume actual speed = x.
5/7 of speed = 5x/7.
Distance = 42,
By applying in the formula
Speed =distance/time.
5x/7 = 42/126/75,
5x/7 = 75 * 42/126 ,
Then we go 5x/7 = 3150/126.
While Criss cross we got,
630x = 22050,
X = 35km/hr.
Kushal said:
5 years ago
5/7 of its actual speed, that's why.
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