Two alloy A and B contain copper and zinc in the ratio 5:11 and 3:5 respectively. If equal weights of the two alloys are melted together to form a third alloy, find the ratio of the weights of copper and zinc in the third alloy.
Answer: B Let xkg of A was mixed with xkg of B to form 2x kg of the third alloy. Weight of copper in the third alloy = 5x/18 + 3x/8 = 11x/16 Weight of zinc in the third alloy = 2x - 11x/16 = 21x/16 The required ratio = 11:21
Q. No. 20:
Two vessels contain alcohol and water in the ratio 3:4 and 65:79. In what ratio should the solution in the first vessel be mixed with the solution in the second, so as to get a solution with alcohol and water in the ratio 4:5?
Answer: A Concentration of alcohol in the 1st mixture = 3/(3+4) = 3/7. Concentration of alcohol in the 2nd mixture = 65/(65+79) = 65/144. Concentration of alcohol in the combined mixture = 4/(4+5) = 4/9. If A and B are the quantities of mixture 1 and mixture 2 that are combined then, by the equation alligation A/B = {(65/144) - (4/9)} /{(4/9)-(3/7)} = 63/144 = 7/16.
Q. No. 21:
A petrol pump owner mixed leaded and unleaded petrol in such a way that the mixture contains 10% unleaded petrol. What quantity of leaded petrol should added to one litre mixture so that the percentage of unleaded petrol becomes 5% ?
Answer: C By alligation rule, 90%.............................100% ...................95%............... 5.................................5 => 5:5 = 1:1 = 1000 ml.
Q. No. 22:
A rabbit on a controlled diet is fed daily 300g of a mixture of two food, food X and food Y. Food X contains 10% protein and Food Y contains 15% protein. If the rabbits diet provides exactly 38 g of protein daily, how many grams of Food X are in the mixture ?
Answer: D Let there are a gm of food X and (300-a)gm of Food Y. Them a*10% + (300-a)*15% = 38 => 10a/100 + (300-a)*15/100 = 38 => 10a+4500-15a = 3800 => a = 140 gm of food X.
Q. No. 23:
In a glass of milk, the proportion of pure milk and water is 3:1, how much of the mixture must be withdrawn and substituted by water so that the resulting mixture may becomes half pure milk and half water ?
Answer: D Milk and water ratio = 3:1 Total = 4 We take half of pure milk and half of water. => 3/2 + 1/2 = 2 Then total remainder = 2/4 = 1/2 unit.
Q. No. 24:
A container contains 120L of milk. From this container, 12L of milk was taken and replaced by exactly equal quantity of water. This process was further repeated two times. How much milk is contained in the container at the end of operation ?