Titration principle is N1V1=N2V2
N = Normality
V = Volume of solution
M1V1n1=M2V2n2
M = molarity
n = Valence factor of acid or base
As pink colour is obtained on consumption of 10ml of Ca(OH)2, we have
20×0.5×1=10×M×2
Molarity of Ca(OH)2=2010=21M
Also, moles of Ca(OH)2=mm of H2SO4
21×20=10×M
Molarity of H2SO4=1M