2 men at same tym start walking towards each other from A n
B 72 kms apart. sp of A is 4kmph.Sp of B is 2 kmph in 1st
hr,2.5 in 2nd, 3 in rd. n so on…when will they meet i in 7
hrs ii at 35 kms from A iii in 10 hrs iv midway
Answer Posted / deepak
After the first hour, they are
4+2=6 km closer to each other. After the second hour, they are
4+2.5=6.5 km closer to each other, and so on. The reduction of distance per hour is therefore an arithmetic progression:
6, 6.5, 7, ...
with initial value a=6 and common difference d=0.5.
The arithmetic series (adding these distances) can be expressed in terms of hours, h, as
S(h) = ah + dh(h-1)/2
= 6h + 0.5(h^2-h)/2
= 6h + (h^2-h)/4
and they meet when this sum equals 72:
6h + (h^2-h)/4 = 72
24h + h^2 - h = 288
h^2 + 23h - 288 = 0
(h - 9) (h + 32) = 0
We have no interest in a negative solution, so the positive one h=9 is the one we want. They meet after 9 hours.
That doesn't match either of the answers that are times, so let's check the distance from A, which at a steady 4 km/h is clearly 36km, half the total distance.
They meet midway (answer iv).
| Is This Answer Correct ? | 7 Yes | 4 No |
Post New Answer View All Answers
2/3 of people read newspaper A,3/4 read newspaper B.if 38 read both and 8 didn't read any of the 2.how many read A?
A person gives a secret to two other persons in 5 minutes. How long will he take to tell the secret to 768 people?
A man has 2 cows of total cost 200 rupees. He sold them for 210. For 1 cow he had a profit of 10% and for the other he had a loss of 10%. What is the price of each cow?
the difference b/w the compound interest payble half yearly and the simple interest on a certain sum cont out at 10% p.a for 1 year is Rs 25 what is the sum
If m-4 is 7 more than n then m+9 is how much more than n+2
govern of irda,sebi and rbi
Difference between the perimeters of two concentric circles is 66. Find the difference between radius.
If a car starts from A towards B with some velocity due to some problem in the engine after travelling 30km.If the car goes with 4/5 th of its actuval velocity the car reaches B 45min later to the actual time. If the car engine fails ofter travelling 45km, the car reaches the destination B 36min late to the actual time , what is the initial velocity of car and what is the distance between A and B in km ans) 20 &
p and q are positive integers with their average 5, find how many different values can p take
A team P of 20 engineers can complete a task in 32 days. Another team Q of 16 engineers can complete the same task in 30 days. Then the ratio of working capacity of 1 member of P to that of a member of Q is:
a train runs first half of the distance at 40 km/hr and the remaining half at 60 km/hr. What is the average speed for the entire journey?
two trains are 2 kms apart. Speed of one train is 20m/s and the other train is running at 30 m/s. Lengths of the trains are 200 and 300m. In how much time do the trains cross each other?
The ratio of no. of boys & girls in a school is 3:2 Out of these what % the boys & 25% of girls are scholarship holders. % of students who are not scholarship holders.?
How can you make a square from two triangles?
box 1 cotain odd value X or Y the box 2 =X i.e 7 or 12 box 3= Y has value 19 if X is 7 or 31 if x is 12 get even value X or Y Use any operator steps allowed 3