Percentage, Avg, profit and loss

                                                              Percentage

Important Concept and Tricks 
1. If x% of A is equal to y% of B, then z% of A=(yz/x)% of B 

2. When a number x is increased or decreased by y%, then the new number will be (100+y)*x/100 

3. When the value of an object is first changed (increased ) by a% and then changed (increased ) by b%,then Net effect=[a+b +ab/100]%

1. In an examination, 49% students failed in English, 36% students failed in Hindi, while 15% failed in both. If total number of passed students is 450, then how many students did appear in the examination? (a) 1800 (b) 2000 (c) 1100 (d) 1500 (e) None of these ANSWER- d 2.Fresh grapes contain 80% water, while dry grapes contain 10% water. If the weight of dry grapes is 500 kg, then what is its total weight when it is fresh? (a) 2350 kg (b) 2085 kg (c) 2255 kg (d) 2250 kg (e) None of the above ANSWER- d
Average

Important Formulae Related to Average of numbers

1. Average of first n natural number=(n+1)/2

2. Average of first n even number= (n+1)

3. Average of first n odd number= n

4. Average of consecutive number= (Firtst number+Last number)/2

5. Average of 1 to n odd numbers= (Last odd number+1)/2

3. The average age of Sachin and Ganguli is 35 years. If Kaif replaces Sachin, the average age becomes 32 years and if Kaif replaces Ganguli, then the average age becomes 38 years. If the average age of Dhoni and Irfan be half of the average age of Sachin,Ganguly , and Kaif ,then the average age of all the five people is: a)28 years b)32 years c)25 years d)30 years e)None of these 4. The average rain fall in the months of January and February is 6 cm and in the months of March to June is 5 cm and July to October is 10 cm and in the November and December, it is 6 cm. The average rainfall for the whole year is: a)7 b)5.5 c)7.5 d)8.5 e)None of these

Profit & Loss

1. If a person sells two similar articles, one at a gain of a% and another at a loss of a%, then the seller always incurrs a loss which is given by

Loss%=(a/10)^2 %

5.A milkman mixes 10% water in pure milk but he is not content with it so he again mixes 10% more water in the previous mixture. What is the profit percentage of milkman if he sells it at cost price:

(a)11.11%

(b)20%

(c)21%

(d)12.1%

(e)None of these

6.A person sold an electronic watch at Rs. 96 in such a way that his percentage profit is same as the cost price of the watch. If he sells it at twice the percentage profit of its previous percentage profit then new selling price will be:

(a)Rs.132

(b)Rs.150

(c)Rs.192

(d)Rs.180

(e)None of these

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