Solution :
==> 2*pi* r = 6600/15 =440m
==> r = 70m
Area = pi*r^2= 22/7 *70*70 = 15,400
Total cost = 15,400*50=7,70,000
Ques 2.
Average weight of 20 men is 72 kgs, and the average weight of 34 women is 62.5 kgs. What is the average weight (rounded off to the nearest integer) of all the men and the women together?
Solution :
Total Weight of men = 20*72= 1440
Total Weight of women = 34*62.5 = 2125
Average weight of all men and women = (1440+2125)/(20+34) = 66.01~ = 66 kgs
Ques 3.
Steve is older than Mark by 4 years. If the ratio of their current ages is 7:9, what will be the corresponding new ratio of their ages when Mark is twice as old as he is now?
Solution :
Ratio difference = 9-7=2 units
Age difference = 4
2 units ---------- 4
7 units --------- ?
Mark age = 14 years
Similarly Steve age = 18 years
Mark is twice as old as he is age = 14 +14 =28
At the same time Steve age = 18+14 = 32
New ratio = 7:8
Age difference = 4
2 units ---------- 4
7 units --------- ?
Mark age = 14 years
Similarly Steve age = 18 years
Mark is twice as old as he is age = 14 +14 =28
At the same time Steve age = 18+14 = 32
New ratio = 7:8
Ques 4.
A, B and C can do a work in 20, 30 and 60 days respectively. How many days does it need to complete the work if A does the work and he is assisted by B and C on every third day?
Solution :
L.C.M of 20,30 and 60 = 60 = Total work
A efficiency = 60/20 =3
B efficiency = 60/30 = 2
C efficiency = 60/60 = 1
A working 2 days and third day they all working together
So total efficiency = A efficiency + A efficiency + A , B and C efficiency ( for 3days )
==> 3+3+6=12
Work completed = 60/12 = 5
Total days = 5*3 = 15 days
Ques 5.
A train has a length of 150 meters . it is passing a man who is moving at 2 km/hr in the same direction of the train, in 3 seconds. Find out the speed of the train.
Solution :
Speed * 10 --------- 36 sec ( its gives how many meters travelled in 36 sec)
Train speed = x kmph
Man speed = 2 kmph
Relative Speed = x-2
(X-2)*10 ----------- 36 sec
150. ----------- 3 sec
==> 30(x-2) = 5400
==> x = 182kmph
Ques 6.
Ravi complete a journey in 10 hours. He travels first half of the journey at the rate of 21 km/hr and second half at the rate of 24 km/hr. Find the total journey in km.
Solution :
Total distance = x km
==> (x/2)/21 + (x/2)/24 = 10
==> X = 224 km
Ques 7.
There are two buildings X and Y. If 15 persons are sent from X to Y, then the number of persons in each building is the same. If 20 persons are sent from Y to X, then the number of persons in X is double the number of persons in Y. How many persons are there in building X ?
Solution :
Case i :
If 15 persons are sent from X to Y, then the number of persons in each building is the same.
==> X-15 = Y +15
==> Y = X -30 ---- (i)
Case ii :
If 20 persons are sent from Y to X, then the number of persons in X is double the number of persons in Y.
==> X+20 = 2*(Y-20) ---- ii
Sub eq (i) in eq ii
==> X = 120
Ques 8.
A sum of money at simple interest amounts to Rs. 850 in 3 years and to Rs. 900 in 4 years. The sum is ?
Solution :
Simple Interest (SI) for 1 year = 900-850=50
Simple Interest (SI) for 3 years = 50 × 3 = 150
Principal = 850 - 150= 700
Ques 9.
A vendor bought bananas at 6 for a rupee. How many for a rupee must he sell to gain 20%?
Solution :
1/6 --------- 100%
1/x --------- 120%
X = 5
Ques 10.
Speed of a boat in standing water is 14 kmph and the speed of the stream is 2 kmph. A man rows to a place at a distance of 4864 km and comes back to the starting point. The total time taken by him is
Solution :
Total time = (4864/(16)) + (4864/(12))
= 304 + 405.33 = 709.33 ~= 709 hrs
