From 86 books to 150 books. An increase of 64 books.
(150 - 86) / 86 = 64 / 86 = 0.744 * 100% = 74.40% or 74% increase
150 / 86 = 1.744 * 100% = 174.40%
86 is the basis. It is 100%
If the problem asks for the value of the percentage increase and the rate is given 74.4% of 86. Then 86 * 74.4% = 64. You just add 64 to 86 to get the new total of books which is 150.
To find the volume, you need to multiply l x w x h
5 x 7 x 10
5 x 7 = 35
35 x 10 = 350
350 is the correct answer
Glad I could help, and good luck!
AnonymousGiantsFan
Multiply your total by your percentage
90 * .80 = 72
72 is the number of questions she answered correctly