50% of all the cakes jenny baked that week were party cakes, 1/5 were fruit cakes and the remainder were sponge cakes what percentage of cakes were sponge cakes

 30% of the cakes were sponge cakes.

Step-by-step explanation:  We are given that 50% of the cakes Jenny baked that week were party cakes, one-fifth were fruit cakes and the remainder were sponge cakes.

We are to find the percentage of cakes that were sponge cakes.

Let n represents the number of cakes that Jenny baked.

According to the given information, we have

Therefore, the number of sponge cakes is given by

Therefore, the percentage of cakes that were sponge cakes is given by

Thus, 30% of the cakes were sponge cakes.