2.54 cm in 1 inch......how many inches in 51.78 cm...
51.78 / 2.54 = 20.4 inches <==
or this way... 2.54 / 1 = 51.78 / x....2.54 cm to 1 in = 51.78 cm to x inches cross multiply (2.54)(x) = 51.78)(1) 2.54x = 51.78 x = 51.78 / 2.54 x = 20.4 inches <==
