Volume of Oil = 10 ml

Density of Oil = 0.91 g/cc

Volume of KOH = 5 ml

Normality of KOH = N/50

So,

Weight of oil = Volume × Density = 10 × 0.91 = 9.1 gms

Now,

$Acid\ value=\dfrac{Volume\ of\ KOH\times{}N_{KOH}\times{}56}{Weight\ of\ oil\ in\ gms}$

$=\dfrac{5\times{}\ 0.02\times{}56}{9.1}$

$=0.615\ …