PERCENTAGE

Australia become the first team to lose by an innings after declaring their first innings closed.......
hahahhahhahahahhahahha
i love it......

OK lets move on to our topic i.e percentage....

today first i will discus one specific type of question based on percentage.....
when there is combination of increase and decrease ( increase+increase , increase+decrease , decrease+decrease)


use positive sign for increase and negative sign for decrease......



lets take an eg. price of petrol increase by 25% but raj wants to spend only 15% more on petrol. so by how much he sud reduced his consumption??????

use the formula =  +25 - X -25X/100 = 15
                           2500 - 1500 = 125X
                                   8% answer...


this method can also be used in population increse , CI when each year have different rate of interest to determine the overall rate...


eg. population of city increases by 10%  in the first year and then decreased by 15 % in the next year. find present population if initial was 10000.

now u can first find the 110% for 1st year then find 85% for next year and give your answer .....
but use the direct formula and solve in no time...........
solution =   10 - 15 - 150/100 
                   -5 - 1.5= -6.5%
this is the overall change in the population over the two year...


QUESTION. price of petrol increase by 25%. by how much % sud use of petrol be decreased to maintain the initial budget....???????????

now as the overall change must be 0 (zero)\

    25 - X -25X/100 = 0
    2500 - 125X = 0
    20 = X
it means use sud decreases by 20%.........

NOW what if there are 3 succesive increases , decrease in the question????????

no problem use the same method twice... two tears at once and then take their answer with last year...

like this.   Q. Population first increased by 10% then decreased by 15% and then increased by 20 over three years. if initial population is 10000 find new population.

10 -15 -150/100 = -6.5 (solved earlier)
  now -6.5 + 20 - 130/100
             20 - 7.8 = 12.2%

NOTE- if there is equal increase and decrease of % then the overall result is ALWAYS negative i.e overall loss happens .... and the answer = square the % and put decimal at two places..

eg.  for 8% increase and decrease the answer will 0.64 (8 square and decimal at 2 places)


some times we come across such question in exam....
Q. a man loses 12.5% of his money and after spending 70% of the remaining , he is left with rs. 210. find his initial money?
 after reading question we know that initial money will be more....
so use the direct formula...





what if in question the initial sud be less???????????? like in this example..........
 Q. dodo deposited Rs. 4800 in locker. in first year he deposited 20% of the amount. in 2nd year he deposited 25% of the increased amount in locker. find the amount in locker at present??????

reading the question tells us that initial money is less... 
so the formula becomes inverse like

NOTE- tomorrow i will take percentage and DI both....

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