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Solution to Problem 6
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In this lesson, problem 6 of mock test paper have been discussed.

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Riya Agarwal
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U
Sir i didn't complete mechanics properly , is it okay to focus more on 12th part of physics ? And is cbse prep good enough for jee mains ?
Udit Gupta
a year ago
for physics it just might be enough. although you would.need the xith portion to be dome as well if you need a good rank in mains..
Spandan Dash
a year ago
Thank you sir
PB
A shorter method for question 24 is to calculate the speeds in km/min. This gives overall speed approx. 1.25 km/min. So if distance between stations is less than 1.25 times the travel time in min, we will consider that for our answer. We can further reduce time taken for calculating individual speeds by converting the 1.25 factor to [1 + 0.25], in other words, [time + one-fourth of time], since it is easy to mentally calculate one-fourth of a number. Eg. for E to F, time = 75 min and distance = 106km. So we have 75*1.25 = 75 + (1/4)75 = 75 + (~)18 =~93. Because 106 > 93, we will not consider this for our answer. This calculation will be even easier for other values of the travel times (100, 80, 120).
ma'am in ques. 24 we take average speed as of ques. 21 but in ques. 21 we find average speed excluding stoppage. so how do we know that in 24 we have to take same speed??
Riya Agarwal
2 years ago
Yes Keshu, you are correct, in this q. 24 we need to consider the overall average speed of the entire trip = (860/ 11.5) = 74.5 kmph, and there are 2 stations for which speed is less than average speed.
Keshu Chhabra
2 years ago
thankew mam.
Is it advisable to solve Q24, as it is so time consuming?
1. CAT DILR MOCKTEST 1

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3. SOLUTION

4. PROBLEM 6

5. DIRECTIONS FOR Q.21 Q.24 A train runs through cities A, B, C, D, E, F G and H. The line graph indicates the time schedule of the train including times of arrival and departure Train schedule 1000 H 860 Z 800 G 750 750 U 700 F IVALUE] 574 E 468 468 2 500 400 300 200 100 D 380 380 231 231 B 140 140 A 0 7:00 8:40 8:50 10:10 10:12 55 2:00 13:20 13:30 1445 15:00 17:00 17:10 18:25 TIME

6. ANSWER THE FOLLOWING: Q21. The overall average speed(in kmph) of the entire trip excluding stoppage time is nearly? (a) 46 km/h (b) 75 km/h (c) 8I km/h (d) 65 km/h Q22. What percentage of time of the entire trip was actually spent travelling between the cities? (a) 76% (b) 42.4% (c) 7.6% (d) 92% Q23. The total stoppage time at the cities in the first half and second half of the total distance is in the ratio Q24. Between how many pairs of consecutive stations does the train run below the overall average speed of the entire trip? (Non- MCo)

7. Q21. The overall average speed(in kmph) of the entire trip excluding stoppage time is nearly? (a) 46 km/h (b) 75 km/h (c) 81 km/h (d) 65 km/h Train schedule 1000 E 900 800 U 700 600 500 H 860 G 750 750 F 574 574 E 468 468 D 380 380 300 200 100 231 231 B 140 140 A 0 07:00 08:40 0850 10:10 10:12 11:55 1200 13:20 13:30 14:45 5:00 17:00 17:10 18:25 TIME

8. Q21. The overall average speed (in kmph) of the entire trip excluding stoppage time is nearly? (a) 46 km/h (b) 75 km/h (c) 81 km/h (d) 65 km/h Solution: The total distance covered is 860 km and the total time taken excluding the stoppage is: (lI hours 25 minutes 52 minutes) 10 hours 33 minutes or 10.5 hours. Hence, the average speed = (860, 105 ) = 8 l .9 = 81 kmph (approximately) Answer: Option (c)

9. Q22. What percentage of time of the entire trip was actually spent travelling between the cities? (a) 76% (b) 42.4% (c) 7.6% (d) 92% Train schedule 1000 E 900 Z 800 U 700 600 500 H 860 G 750 750 F 574 574 E 468 468 D 380 380 300 200 100 231 231 B 140 140 A 0 07:00 08:40 0850 10:10 10:12 11:55 1200 13:20 13:30 14:45 5:00 17:00 17:10 18:25 TIME

10. Q22.What percentage of time of the entire trip was actually spent travelling between the cities? (a) 76% (b) 42.4% (c) 7.6% (d) 92% Solution: The total time of the journey is I hours 25 minutes and the travelling time excluding the stoppage time is 10 hours 33 minutes Hence, the required percentage is [(1 0.5 / 1 1 .5) * 1 001-91 .3%-92% Answer: Option (d)