500
Frederickson is back and now he is arguing with Sandy. Sandy says that the ratios 10:20 and 21:42 are not equivalent and do not form a proportion. Frederickson says that they do form a proportion. Who is right?
What is Frederickson?
10:20 and 21:42 form a proportion, which you find when you cross multiply and get the same product of 420 across both diagonals.