2.5cm = 1 inch. To figure out what 3 quarters ( 3/4 ) of an inch is, divide 2.5 by 4 then multiply by 3. ( 2.5/4 x3 ) This equals 1.9cm. There are 17 blocks so multiply 1.9 by 17. ( 1.9/17 = 32.3) 30 cm = 12 inches. 2.3 is 90% of 2.5, so add 0.9 to 12.
