Advertisements
Advertisements
प्रश्न
Along a road lie an odd number of stones placed at intervals of 10 m. These stones have to be assembled around the middle stone. A person can carry only one stone at a time. A man carried out the job starting with the stone in the middle, carrying stones in succession, thereby covering a distance of 4.8 km. Then, the number of stones is·
विकल्प
35
15
31
29
उत्तर
31
Explanation:
Let the number of stones = n
The distance between every stone = 10 m
So, here an AP is formed, a = 20, d = 20
`="n"/2[2"a"+("n"-1)"d"]`
Diatance between in both side,
`⇒4800=2("n"/2 2"a"+("n"-1)"d")`
⇒ 4800 = n[2 × 20 + (n − 1)20]
∴ n = 15 (on one side)
Then, the number of stones on both side
= 2 × 15 = 30
∴ Total number of stones
= 30 + 1 (middle stone) = 31
APPEARS IN
संबंधित प्रश्न
A man can row 14 km/hr in still water. ln, the stream flowing with the speed of 10 km/hr he takes 4 hours to move with the stream and come back. Find the distance he rowed the boat.
A train 300 meters long is running at a speed of 25 meters per second, it will cross a bridge 200 meters long in
Pipe A can fill a tank in 10 hr and Pipe B can fill the same tank in 12 hr. Both the pipes are opened to fill the tank and after 3 hr Pipe A is closed. Pipe B will fill the remaining part of the tank in:
A and B walk from X to Y, a distance of 27 km at 5 km/hr and 7 km/hr, respectively, B reaches Y and immediately turns back meeting A at Z. What is the distance from X to Z?
A man can row 5 km/h in still water. If the speed of the current is 1 km/h, it takes 3 h more upstream than in the downstream for the same distance. The distance is
Robert is travelling on his cycle and has calculated to reach point A at 2 pm if he travels at 10 km/h, he will reach there at 12 noon if he travels at 15 km/h. At what speed must he travel to reach A at 1 pm?
A boat takes 90 min less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 m/h, the speed of the stream is
Sita and Geeta start at the same time to ride from place A to place B, which is 90 km away from place A. Sita travels 3 km per hour slower than Geeta. Geeta reaches place B and at once turns back, meeting Sita 15 km from place B. Geeta's speed (in km/h) is:
A man crosses a road 250 metres wide in 75 seconds. His speed in km/hr is :
A train goes from Gandhinagar to Patna at a speed of 128 kmph and returns to Gandhinagar at a different speed. If the average speed for the entire journey is l 12 kmph, then find the speed of the train for the return journey (to nearest kmph)
