barry had a pan of brownies 2/5 full his friends came over and ate 1/4 how much is left
2 / 5 = 4 / 10 = 0.4
1 / 4 of 0.4 = 0.1
0.4 - 0. 1 = 0.3 = 3 / 10 = 30 / 100 = 30 %
OR
1 - 1 / 4 = 3 / 4
( 2 / 5 ) * ( 3 / 4 ) = 6 / 20 = 2 * 3 / ( 2 * 10 ) = 0.3