Question

Sean has 1/5 of a cupcake and 1/5 of a large cake . Are the wholes the same? Explain.

Answer 1

No, the only way I can explain it is with actual numbers. 50% of 100 is not the same as 50% of 200. Though the ratio may be the same, the wholes are not the same. 

Answer 2

I don't think the wholes are the same because if you imagine a cup cake and a cake of different sizes cut into equally 5 pieces, one piece of the cup cake won't be the same size as the piece of cake.
or fractions are to show the fractions of something, so just because two fractions are the same it doesn't mean the whole numbers are the same too.