Ashok a master adulterator cum grosser sells haldi powder (turmeric powder), which contains fivepercent saw dust. What quantity of pure haldi should be added to two kilos of haldi (containing fivepercent saw dust) so that the proportion of saw dust becomes four percent?
Answer: C Pure haldi has 0% saw dust and the adulterated sample has 5% saw dust in it. By adding appropriate amount of pure haldi, the concentration of saw dust, in the 5% sample, can be reduced to 4 %. Applying allegation: 5%..............................0%(Pure haldi) .................4......................(Resultant) 4..................................1 (Ratio) => 4/1 = 2kg(of 5% sample) /Pure haldi => Pure haldi = 0.5 kg.
Q. No. 26:
In a mixture of 35 litre, the ratio of petrol to alcohol is 4:1. If 7L alcohol is added to the mixture, the ratio of petrol to alcohol changes to a new ratio. If we want the ratio of petrol to alcohol to change back to the original value, how much petrol is to be added now?
Answer: B In order to keep the solution of the same ratio, we need to add petrol in the same ratio as already there in the solution i.e, we need to add = 4/1 * 7 = 28 L
Q. No. 27:
A girl has 1L of solution that contains orange juice and water in the ratio 3:1. She adds 250ml of 3:2 solution of orange juice and water to it and then use 250ml of the combined mixture to make complete juice. How much of pure juice is she left with?
Answer: D In a mixture 1000 ml, orange juice: water = 3:1 Hence, orange juice = 750 ml and water = 250 ml A 250 ml of 3:2 solution contains 150 ml of juice and 100 ml water. Total juice = 900 ml , total water = 350 ml After using 250 ml to make impure juice used = 250/1250 * 900 = 180 ml Pure juice left = 900 - 180 = 720 ml
Q. No. 28:
Several litres of Water were drawn from a 54 L vessel full of water and an equal amount of acid is added. Again the same volume of the mixture was drawn off and replaced by acid. As a result, the vessel contained 24L of pure water. How much water was drawn off initially?
Answer: C 54(1- x/54)2 =24 => 1- x/54 = 2/3 x= 18 L
Q. No. 29:
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. 30:
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.