Question: In a library 20% books are English, 50% of remaining are French and 30% of remaining are Latin. The rest 6300 are in regional languages. What's the total no. of books?
Answer: Let total books = x
Then no. of books in English= 20% of x= x/5
French = 2x/5
Latin = 3x/25
x-(x/5+2x/5+3x/25)=6300
Therefore x=22500
Another shortcut to solve this question using percentages is given as follows:
6300(100/100-20)(100/100-50)(100/100-30)= 22.500
I dont understand this shortcut. The Formulae that i've been given are:
To calculate % increase or decrease:
actual increase/original amount*100%
actual decrease/original amount*100%
If the price of something is increased by R%, then reduction in consumption so as not to increase the expenditure /OR/ If A is R% more then B, then B is less than A by:
[100*R/(100+R)]%
And the reverse of the above:
[100*(R/(100-R)]%
The part that i'm confused about in Shortcut solution is the application of the formulae.
IF "(100/100-20) (100/100-50) (100/100-30)" Is derived by applying one of the formula, then HOW has it been done? What is "100"?
Please Explain
Thank you