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
Advertisements
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
Choose the most appropriate option:
A train which is moving at an average speed of 40 kmph, reaches its destination on time. When its average speed reduces to 35 kmph, then it reaches its destination 15 minutes late. The distance travelled by train is:
Choose the most appropriate option
A man rows to a place 45 k.ms distant and back in 12 hours. He realises that he can row 5 k.ms downstream at the same time as 3 k.ms against the stream. The velocity of the stream is:
Solve the following question and mark the best possible option.
A person can swim in still water at 4 km/hr. If the speed of water is 2 km/hr, how many hours will the man take to swim back against the current for 6 km?
The Bubna dam has four inlets. Through the first three inlets, the dam can be filled in 12 minutes; through the second, the third and the fourth inlet, it can be filled in 15 minutes; and through the first and the first inlet, in 20 minutes. How much time will it take all the four inlets to fill up the dam?
There is a leak in the bottom of a tank. This leak can empty a full tank in 8 hours. When the tank is full, a tap is opened into the tank which admits 6 litres per hour and the tank is now emptied in 12 hours. What is the capacity of the tank?
If a person walks at 14 km/h instead of 10 km/h, he would have walked 20 km more. The actual distance travelled by him is
A boat running upstream takes 8 h 48 m to cover a certain distance, while it takes 4 h to cover the same distance running downstream. What is the ratio between the speed of the boat and the speed of the water current respectively?
It takes eight hours for a 600 km journey. if 120 km is done by train and the rest by car. It takes 20 min more if 200 km is done by train and the rest by car. The ratio of the speed of the train to that of the cars is
A car consumes 5.4 litres of petrol to cover 60.48 km, how many kilometers be covered with 22 litres of petrol?
The length of a train and a platform is equal. The train at the speed of 90 km/hr crosses the platform in 1 minute. What is the length of platform?
