Converting each of the given fractions into decimal form, we get,5/6 = 0.838/15 = 0.532/3 = 0.663/4 = 0.754/5 = 0.86/7 = 0.85Clearly, 0.85 does not lie between 0.83 and 0.53Hence the required fraction is 6/7.
Let the total length of pencil = L cm Then, black part = L/8∴ Remaining part = L - L/8 = 7L/ 8 and White part = (7L/8)/2 = 7L/8∴ Remaining part = L - (L/8 + 7L/16) = 7L/16∴ length of blue part = 7L/16According to the question, 7L/16 = 31/2⇒ 7L/16 = 7/2 ∴ L =8