A 735 gm sample of a 16% (by weight) solution of antiseptic in water is kept for a week days. Some of the water gets evaporated and the concentration of the solution becomes 20% (by weight). what amount of water gets evaporated?
Answer: B Amount of 16% antiseptic in the mixture = 735*16/100 gm Now the amount of antiseptic becomes 20% of the mixture Amount evaporated = 735 - (735* 16/100* 100/20) = 147 gm.
Q. No. 8:
A vessel contains 12L Vodka and another contains 4L whisky. 3L is removed from each of the vessels and transferred into the other. The same operation is replaced once more. What is the final ratio of vodka to whisky in two vessels?
Answer: C Ratio of vodka to whisky in the 1st vessel transfer is (12-3):3 = 3:1 Ratio of vodka to whisky in second vessel after 1st transfer is 3: (4-3) = 3:1 Since, the ratio of vodka and whisky in both the vessels is equal. Any amount of such exchnages any number of times will not alter the ratio of vodka to whisky.
Q. No. 9:
How many kilograms of tea worth Rs 25 per kg must be blended with 30 kg of tea worth Rs 30 per kg so that by selling the blended variety at Rs 30 per kg there should be a gain of 10% ?
Answer: A There are two varieties of tea. One worth Rs 25 per kg and other worth Rs 30 per kg. Now, by selling the blended variety at Rs 30 per kg, profit should be 10%. So, the cost price of the blended tea should be 30/1.1 = Rs 300/11 per kg. By alligation rule, 25...........................30 .........300/11............. x.............................y We get, x/y = 30/25 Amount of tea of rs 30 per kg to be used is 30kg. If the amount of tea worth Rs 25 per kg is a. 30/25 = a/30 a = 36 kg.
Q. No. 10:
On test-tube contains some acid and another test-tube contains an equal quantity of water. To prepare a solution, 20g of the acid is poured into the second test-tube. Then, two-third of the so-formed solution is poured from the second tube into the first. If the fluid in the first test-tube is four times that in the second, what quantity of water was taken initially ?
Answer: D From options :- Let the tube contains 100g of Acid and 100 gm water. 1st operation = Acid (100-20)gm and Water (100+20)gm II nd operation = Acid (80 + 120*2/3) and Water (120/3 = 40 gm) Ist is 4 times the 2nd.
Q. No. 11:
There are two vessels of equal capacity, one full of milk, and second one-third full of water. The second vessel is, then filled up out of the first, the contents of the second are then poured back into the first till it is full and then again the contents of the first are poured back into the second till it is full. What is the proportion of milk in the second vessel, if capacity of the vessel is 20L ?
Answer: B Amount of liquid left after n operations, when the container originally contains x units of liquid from which y units is taken out each time is x(1- y/x)n units. Here, x= 20L, y = 20*2/3 = 40/3 and n= 3. => 20 (1- (40/3)/20)3 = 20 (1- 2/3)3 = 20/27.