50% of all the cakes jenny baked that week were party cakes, 1 fifth were fruit cakes, and the remainder were sponge cakes. what percentage of cakes were sponge cakes?

-According to the sentence, 50% of all the cakes were party cakes, so: Party cakes 50%

-1 fifth were fruit cakes, so: 1/5x100= Fruit cakes 20%

-The remainder were sponge cakes: 100-50-20= Sponge cakes 30%

The percentage of cakes that were sponge cakes was 30%, as 50% were party cakes and 20% were fruit cakes.