What will be the new volume when 128 ml of gas at 20.0°c is heated to 40.0°c while pressure remains unchanged?

The relation between the volume, pressure and temperature of gases is shown using the following equation:

(pressure x volume) 1 / temperature1 = (pressure x volume) 2 / temperature2

This relation is actually established by combining the three gas laws (Boyle's, Charles's and Gay-Lussac's)

At constant pressure,

(volume/temperature) 1 = (volume/temperature) 2

128/20 = v2/40

Volume = 256 ml