1. If pipe A can fill the tank in 45 minutes and pipe B in 30 minutes, find the time to fill the tank if both the pipes are opened together.
A. 12 minutes
B. 20 minutes
C. 18 minutes
D. 15 minutes
Answer: Option C
Explanation:
In 1 minute pipe A can fill [latex]\frac{1}{45 }[/latex]th part of the tank and pipe B can fill [latex]\frac{1}{30 }[/latex]th part of the tank. If they are opened simultaneously then in 1 minute they can fill ([latex]\frac{1}{45 }[/latex]
+ [latex]\frac{1}{30 }[/latex]) part of the tank = [latex]\frac{1}{18 }[/latex]th part of the tank.
Hence, in 18 minutes the tank gets filled if pipes A & B are opened together.
2. Find the ratio in which wheat of inferior quality (Rs.14/kg) be mixed with the wheat of superior quality (Rs.28/kg) so that the shopkeeper gains Rs.2 by selling the resulting mixture at Rs.20/kg.
A. 1 : 3
B. 5 : 2
C. 3 : 4
D. 2 : 5
Answer: Option B
Explanation:
Let the resulting mixture be 1 kg, and x kg be the amount of wheat of inferior quality.
Therefore, (1-x)kg is the amount of wheat of superior quality.
As the shopkeeper gains Rs.2, the cost of the mixture is Rs.18
14*x + 28*(1-x) = 18
14x - 28x + 28 = 18
14x = 10
x = [latex]\frac{5}{7}[/latex]
(1 – x) = [latex]\frac{2}{7 }[/latex]
x : (1-x) = [latex]\frac{5}{7 }[/latex] : [latex]\frac{2}{7 }[/latex]
= 5 : 2
3. Find the area of the square field if a train 800 meters long passes the field with a speed of 120 kmph in one minute.
A. 1.44 sq. km
B. 4 sq. km
C. 2 sq. km
D. 2.64 sq. km
Answer: Option A
Explanation:
120 km/hr = 120 * [latex]\frac{5}{18 }[/latex] = 33.33 m/s
v = [latex]\frac{d}{t }[/latex] ; 33.33 = [latex]\frac{d}{60 }[/latex]
d = 2000 m
Hence, in one minute the train travels 2000 m. But, as the train is 800 m long and it passes the field, the length of the field is 2000 – 800 = 1200 m.
Area = 1200 * 1200 = 1.44 sq. km
Therefore, It takes B [latex]\frac{8}{3}[/latex] hours to catch up with A. Distance: [latex]\frac{8}{3}[/latex] x 10 = [latex]\frac{8}{3}[/latex] km = 26.67
4. If the ratio of present ages of Jeet and Jay is 5:7 and after 6 years the ratio will be 3:4, what is the present age of Jay?
A. 42
B. 30
C. 36
D. None of these
Answer: Option A
Explanation:
As the present age of Jeet and Jay are in the ratio 5:7, let their ages be 5x and 7x respectively.
Therefore, their ages after 6 years will be (5x+6) and (7x+6) respectively.
Now, it is given that [latex]\frac{(5x+6)}{(7x+6)}[/latex] = [latex]\frac{3}{4}[/latex]
4*(5x+6) = 3*(7x+6)
x = 6
Hence, the present age of Jay is 7x = 7*6 = 42 years
5. A military camp has a food reserve for 250 personnel for 40 days. If after 15 days 50 more personnel are added to the camp, find the number of days the reserve will last for?
Answer: Option C
Explanation:
As the camp has a reserve for 250 personnel that can last for 40 days, after 10 days the reserve left for 250 personnel is for 30 days. Now 50 more personnel are added
in the camp.
Hence, the food reserve for 300 personnel will last for:
250:300::x:30 ……..(it is an indirect proportion as less men means more days)
x = [latex]\frac{(250*30)}{300}[/latex]
x = 25 days