If permissible compressive stress in concrete in-bending for M20 grade of concrete is 7 N/mm², then modular ratio will be : 

Concept:

Modular ratio (m):

The value of modular ratio m is given below;

\(m={E_s\over E_c}={280\over 3σ_{cbc}}\)

Where σ_cbc = permissible compressive stress due to bending in concrete N/mm², E_s = modulus of elasticity of steel, and E_c = modulus of elasticity of concrete. 

Calculation:

Given

Grade of concrete is M20

Permissible compressive stress (σcbc) = 7 N/mm²

Modular ratio (m) = \({280\over 3\sigma_{cbc}}={280\over 3\times 7}=13.33\)

Modular ratio (m) is 13.33. Hence option (2) is the correct answer.