Hello Prasad !

Formula for Volume of cuboid is , (length × breadth × height) cubic units.

So , if length is  increased by 20% which means new length is 1.2 time of old length , similarly , new breadth will become 1.1 time more and height will become 0.95 times of old height , as it decreased.

So now , new volume will become , 1.2 * length × 1.1*breadth × 0.95*height ,

1.254 * length × breadth × height ,

Which means it get increased by 25.4 %

Hope it helps !