10 books because the ratio is 2:5 and you have 4:x so x=10 ((:
Ray should buy the first one because it has the greater volume by 1,440 square inches.
Tank 1: 20x20x18=7,200
Tank 2: 40x12x12=5,760
7,200-5,760=1,440
Pythagoras
28^2-19^2= 423
Square root of 423 = 20.5669638
Answer = 20.5669638
